Equine Color Genetics 101

An overview of common equine colors and the genes that cause them

Written by Sara LaFlamme
There are so many people out there who will call a black sabino a blue roan, or a chestnut sabino a red roan, and then there are the ever-confusing things with color like chestnut vs. sorrel. I have decided to create this section on our website in order to help anyone out there who wants to learn understand equine color genetics. Not many people realize how important it is that we get the colors right when registering horses - it is for the next generations, to enable them to search back through their horse's recorded pedigree, and be able to accurately determine the genes their horse carries (or might carry). We will never be able to do that if horses are registered under the incorrect colors. I have seen such things as a filly by Out on Parole registered as a smoky cream...this is not physically possible and everyone should know that much, but sadly they do not. It is situations such as that which have inspired me to create this page.

I will begin by giving an overview of the base colors, then the pattern genes, then the dilution genes. All of these genes can be found in Tennessee Walking Horses.

*Genetic Terminology:

Gene - heritable portion of DNA that codes for a specific trait (i.e. coat color)

Allele - different forms of the same gene

Homologous Pair - set of chromosomes that contain genes which code for the same trait (i.e. coat color) - one chromosome would be recieved from a maternal donor (mother) while the other was recieved by the paternal donor (father). These chromosomes are the same in size, and contain genes that code for the same traits, with the same gene loci.

Genotype - genetic makeup of the horse

Phenotype - physical appearance; physical expression of genes

Dominant - only requires one copy of the gene (one allele) to code for a particular trait for it to exert a phenotypic effect.

Recessive - requires 2 copies of a gene (homozygous - same alleles) in order to exert phenotypic effect.

Homozygous - carries 2 copies of the same allele on a homologous pair

Heterozygous - horse carries 2 different copies of an allele on a homologous pair

*Key to reading genotypes:

(Capital letters represent dominant genes, small letters represent recessive genes and/or the lack of a dominant gene.)

E - black

e - chestnut

A - agouti (the gene that restricts black to the points - causes bay)

At - the form of agouti that causes brown

a - non-agouti

TO - tobiano

O - frame (lethal white) overo

SB1 - Sabino (most common form)

Spl - Splashed white overo (splash)

CR - Cream dilution

CH - Champagne dilution

D - Dun dilution

Z - Silver dilution

Rn - Roan modifier

G - grey modifier

n - gene not present

*Keep in mind that all genes come in pairs. For example, a horse's genotype will always read in this format: EE Aa and so on and so forth if the horse carries tobiano, cream, etc.

For example... 
EE AA represents a homozygous (carrying two copies of the same gene) black, homozygous agouti horse

ee Aa represents a chestnut (notice it requires two of the recessive chestnut genes to cause the horse to be chestnut) horse that is heterozygous (carries one copy of a gene) for agouti.

Ee Aa nCr represents a heterozygous black, heterozygous agouti, and heterozygous cream horse. (Phenotype would be buckskin)

Now that you understand how to read genotypes, keep reading to learn about the genes that cause (almost) every color known in the equine species. 

I.) Base Colors

Underneath every palomino, champagne, tobiano, and true roan there is a plain old bay, chestnut, or black - the "base" colors. It is the horse's base color that determines whether it will be a palomino or buckskin, a classic champagne or an amber champagne, or a "blue" roan or a "red" roan.

A. Chestnut. A chestnut horse carries two recessive chestnut genes (ee). A chestnut horse never carries black, but may carry agouti (A). Since agouti only affects the black (E) gene, a chestnut horse can carry agouti without expressing that gene. A chestnut horse always has the genetics ee Aa or ee AA. A chestnut may come from two chestnut based parents, two black based parents, or any mix of the two.
Oh, and by the way - chestnut and sorrel are 100% the same thing - there is absolutely no difference whatsoever genetically between the two. So I have used the terms interchangeably on this site, but have recently begun to stick to using chestnut only to avoid confusing things. 

This mare, Extravagant Ritz, is a great example of a chestnut (ee) carrying absolutely not one single other modifying gene. Her genetics read ee aa. This is what a chestnut horse looks like stripped of all other modifying genes.

B. Black. A black horse carries at least one black (E) gene, and never carries agouti (A). The lack of the presence of agouti is what allows the black pigment to be distributed evenly over the horse's body, causing a black based horse. A black horse's genetics will always read EE aa or Ee aa for the base color. A black based horse must always have one parent that was either black based (in other words, carried a black [E] gene - could be black or bay). Since a black horse never carries agouti (A), they can never come from two homozygous agouti (AA) horses.

This mare, High Fare, is a wonderful example of a black base with no additional genes. This is what a black horse looks like on its own and her genetics read Ee aa.

...The base colors affected by modifiers...

A.) Bay.  Bay is not technically a base color, since it is caused by an agouti modifier affecting a black base. A bay horse carries at least one copy of the black gene (E) and at least one copy of agouti (A; it restricts black to the points). Therefore, a bay or bay "based" (buckskin, amber champagne, bay dun, bay tobiano, etc. etc.) horse will always have genotypes that read as follows: EE AA; Ee AA; Ee Aa; or EE Aa. A bay based horse MUST have one parent that carries black and one parent that carries agouti. For example, you will NEVER get a bay foal from two chestnuts or two blacks; the chestnut horses don't carry black (E) and the black horses don't carry agouti (A).

This Cleveland Bay horse is a bay. His genotype likely reads EE AA. 

B.) Brown. Similar to bay, brown is a black base affected by a different form of the agouti modifier. Also called seal brown, brown is characterized by mostly dark tones, with lighter tones around the flank, girth, and muzzle areas. Brown is often mistaken for sun faded black, smoky black, or dark bay.

II. Pattern Genes

So, you ask, what causes that blaze on my horse's face? How about a snip or a star? What genes make a horse "spotted"? Get ready for me to take you through the wonderful "pattern" genes - sabino, splash, tobiano, frame - the genes that cause the white markings we find on our horses.

>> The "Overo" Genes
The term "overo" is a broad term used to describe any gene that causes white markings on a horse, other than tobiano. There are three main types of overo: Sabino, Splashed White, and Frame (a.k.a. Lethal White). 

A.) Sabino. Sabino is probably the gene responsible for most white markings. It is thought that, in its most minimal form, sabino can cause a simple star and nothing else. In its most common form, a sabino carrier will have a blaze, several socks or stockings, and perhaps even some roaning. In its extreme forms, sabino will cause a black based horse to appear "grey" and "spotted." This is where people often make their critical errors in registering their horses by an incorrect color. Everyone should be aware that sabino CAN and DOES cause roaning, but you are using incorrect color terminology if you call a heavily roaned black sabino a "blue roan." The term "roan" is only to be used in describing a horse's color when a horse carries the "true" roan gene.
There currently is a test for one form of sabino - probably the most common form in Walking Horses - genetically labeled SB1. It is believed that there are several forms of sabino, so a horse with only a small star may test negative for SB1, but the star could still be caused by sabino - just a form other than SB1.

This horse is tested positive for SB1. This is a common expression of the SB1 gene. Genetically, this horse is Ee aa nSB1

This mare, Motown's Devil Woman, is another "typical" sabino. She has white in the places sabino likes to put it - both hind legs and the face - and she also has some sabino caused roaning throughout her body that you can see when you meet her in person. 
Her genotype is ee aa nSB1 

Chromette is the perfect example of a "loud" sabino. She has high stockings, a bald face, tons of roaning, and multiple areas of "spotting" caused by the sabino. Her genotype - Ee aa nSB1 

All of the above horses are heterozygous sabinos - each carries only one copy of the sabino gene. In the case of a horse that is homozygous for (carries two copies of) the sabino gene, we get what is commonly referred to as a "maximum white" sabino. A maximum white sabino will usually be around 90% white with some spots of color. If a horse carries two copies of the SB1 gene, it will ALWAYS be a maximum white sabino, regardless of whether the parents were as loud as Chromette or extremely minimal. Below is a maximum white sabino (SB1SB1) Tennessee Walking Horse:

B.) Splashed white. "Splash" as it is commonly known is one of my favorite pattern genes. Like sabino, it can be expressed in either very minimal form or very "loudly." There is currently a test for splash offered at UC Davis that tests for 3 different alleles known to cause the "splashed white" phenotype (SW1, SW2 and SW3). Like sabino, there are thought to be more forms yet of the gene. Splash is the gene primarily given credit for markings such as snips and front socks. Like sabino, splash expresses differently in homozygous form. Splash is extremely prevalent in the Tennessee Walking Horse. It can be found in nearly all bloodlines, particularly through the Pride of Midnight/Prides Generator lines, as well as 2 of Generator's most prolific sons - The Skywatch and Gen.'s Major General. (These are just the lines that come to mind as being major splash producers).
Characteristics of splash include bottom-heavy white; the idea of splash is that the horse was "dipped in white paint." The edges to the white are smooth and rounded, unlike the jagged edges sabino typically causes. Splash is often the cause of blue eyes in horses (particularly Walking Horses), and is genetically indicated as Spl. 

Lucky to be a Lady is a great example of a minimal splash. Notice her facial marking; she has a small star which breaks off, then about halfway down her face a strip begins, growing thicker until it becomes a large snip covering nearly all of the space between her nostrils. This is a "bottom heavy" facial marking, a characteristic that strongly indicates splash. Her bloodlines also back up the fact that splash is causing her white rather than sabino - she is a sister to The Skywatch (noted splash producer) through her dam, Lady Fame, has very obviously splash markings nearly identical to her own. Her brother, The Skywatch, is very well known for producing foals with a lot of face white, front socks (look at Watch it Now), and often blue eyes - all splash characteristics. Her sire, Gen's Armed and Dangerous, is another splashed white by Prides Generator.  

Another example of splash I wanted to point out is Miss Magnolia. She has a small snip, a good bit of white on her lower lip, and a front sock. The front sock is a great indicator of splash - this gene loves to put white on the front legs more so than sabino. Also, Miss Magnolia is by Gen's Major General. 

This horse is a wonderful example of the markings that splash will typically cause. I will not go into his genotype as he likely carries 2 dilution genes which will not be discussed until later.

Here is a very loud splashed white horse. Notice the "bottom heavy" markings are still evident; it looks as though the horse were dipped in white paint. This is "Gambling Man," a very famous Paint Horse.
(Also notice the "moustache" on his lips, a trademark of splash.)



ABSOLUTELY CLASSIC bottom-heavy face white, four smooth-edged white socks on this Appaloosa stallion. Tested heterozygous for splash, n/SW1

This is "Spooks Gotta Whiz" - tested heterozygous for both SW1 and SW2. In other words, n/SW1 n/SW2.

Miss TD Kid, Paint mare who is one of the few tested SW3 horses. n/SW3.

AND......are you wondering JUST how minimal splash can be?? This guy is tested positive SW1. n/SW1
He was only tested because he produced a foal with a very obvious splash phenotype out of a mare who tested NEGATIVE for splash (although the mare herself looked like a good candidate to test for splash - which, I'm sure, is why they did!).

C.) Frame Overo. Frame is the gene most commonly associated with the term overo. Frame is very rare in Tennessee Walking Horses, and much more difficult to breed for than the other pattern genes because, not only can a horse minimally express the gene to the point of being completely solid, but frame in its homozygous form is lethal (hence, lethal white overo). Therefore it is not wise to breed a frame carrier to another frame carrier (since then you would be risking the chance of getting a Lethal White foal), and typically you have a less than 50% chance of getting the desired color when breeding for frame (since minimal expressions of the gene are always possible).
Frame, when expressed, is really quite easy to identify. The color is characterized by dark legs, color over the topline - hence, the white is "framed" with color and typically stays on the horse's sides, lacking the presence of other genes. Frame does cause face white and blue eyes, but is NOT known to cause leg white. A horse carrying frame overo and nothing else (assuming the horse is not a minimally expressed frame) will have no socks, stockings, coronets, etc. Like splash and most other color patterns, frame can be completely minimal - there are tested frame overo (LWO) horses who do not have a white hair on their body!

Here is a chestnut based frame overo (ee aa nO).

    >>Frame + Other Overo Genes
Frame is commonly found with other pattern genes.

*Frame + Sabino
Frame is an easy pattern to identify, but when the horse has white legs you must always remember that it is carrying another gene, since frame likes to keep color on the legs. A frame horse who also carries sabino will maintain the lacy edges to the white spots, a characteristic of both frame and sabino. Since frame causes face white and blue eyes, it is not reliable to look at the face white to determine what genes the horse carries - look for the leg white. Remember, sabino likes to keep white on the hind legs most of all, while splash prefers the front legs. If a horse has one or two high hind stockings, and lacy white edges, it is a good bet that horse is frame + sabino.

See the frame and sabino characteristics? Ignoring the dilution genes that are very obviously at work on this guy, he is likely ee aa nO nSB1

*Frame + Splash
A frame horse carrying splash will often, but not always, have leg white. Look for the rounded edges to the color, and often a greater amount of white than frame alone would cause. Since frame and splash are both overo genes, no white should cross the topline.

Despite his lack of front leg white, this horse is obviously splash + frame rather than sabino + frame, evidenced by the smoother edges to the color and lack of sabino roaning. (*Sabino roaning is not always necessary for a horse to be sabino, but the lack of it does still further support the presence of splash rather than sabino.) This horse could be ee Aa nO nSpl

*Frame + Sabino + Splash
When a horse carries all 3 overo genes, it will have a great amount of white. Look for characteristics of all 3 genes - white over the topline, sabino roaning, leg white, etc. The smoothness of the edges is not such a reliable indicator of what genes are at work at this point. 

Frame + Sabino + Splash. Notice the great amount of white. The edges are jagged but not quite as much as the Frame + Sabino horse; splash is helping to smooth them out. The white leg could be caused by sabino or splash, or possibly both. This horse has plenty of sabino roaning evident. I'd write his genotype (completely guessing on the agouti status) as ee Aa nO nSB1 nSpl

D. Dominant White. Dominant white is an overo gene most similar to sabino. Like sabino (and splash) there are many different alleles known to cause the DW phenotype - over 10 so far. Also like sabino, DW is known to be caused by a mutation on the KIT chromosome. It causes rough, jagged edges like sabino, but is generally a much "louder" pattern similar to an extensive (homozygous) splashed white. Dominant white can also cause a horse to be completely white.

These two horses are dominant white Thoroughbreds. Notice they have pink skin, which distinguishes them from a grey, but unlike double-dilute (homozygous) cream horses, which look similar in phenotype, these horses' eyes are dark as opposed to clear blue.
Due to the complete lack of pigmentation, it is impossible to tell without parental information and/or genetic testing (in other words, it is impossible to tell based on phenotype alone) the base colors of these horses.

Puchilingui, a Dominant White Thoroughbred. DW can express moderately, or loudly, like the previous genes we have discussed. Notice the similarities to sabino.

>> Tobiano. Tobiano is another of my favorite pattern genes. It is one of the most sought-after color patterns and, unlike its overo counterparts (sabino, splashed white, and frame are all forms of overo), tobiano is a pattern gene that breeds "true." In other words, you don't have to test a horse to see whether it carries tobiano - if it carries this gene, it will exhibit the pattern. 
Let's set the first rule of tobiano in stone before we go any farther: tobiano does NOT cause face white. A typical expression of tobiano (when tobiano is the only gene present on the base color) includes 4 white legs (tobiano will ALWAYS cause the white legs, and it is very rare to come across a tobiano with even one solid leg), and large, rounded spots. Tobiano typically tries to keep color over the head, flanks, and chest above all else. 

Like the other pattern genes, tobiano can be expressed in minimal form. Below is an example of a minimal tobiano. Notice the lack of face white despite having 4 high stockings. Had another gene such as splashed white or sabino caused this magnitude of leg white, the horse would certainly have a good amount of facial white and likely white coming up from the belly as well. This horse has a brown base with only tobiano acting on it. I do not know his pedigree, so the best I can put his genotype down as is E? A? ?TO.

Here is a typical expression of tobiano. Notice the lack of face white - this is what tobiano itself does. If there were face white, we'd know this horse was carrying another gene to cause it. Also notice that there is color over the flank, chest, and head. E? aa ?TO

   >>Tobiano + other pattern genes
Tobiano is often found along with other pattern genes, namely the overo genes (sabino, splashed white, and frame). Any mix of tobiano + an overo gene is called non-specifically a tovero.

*Tobiano + Sabino
This tovero combination is caused by tobiano and sabino acting on the same horse. Notice the horse has color over the flanks, chest, and head, indicating tobiano. Sabino can be identified according to the blaze on the horse's face (remember, tobiano does not cause face white) and the jagged edges of the spots (tobiano produces nice rounded spots - sabino has the lacy edges). Often there will be roaning on a tobiano/sabino, further indicating the presence of sabino.
*One particularly interesting aspect of tobiano/sabinos is that if you have one, that horse will always throw a tobiano or sabino offspring, but never both unless the other parent contributes the necessary gene to make it so. Since tobiano and sabino are mutations of the same gene, they are adjacent alleles on a homologous pair; thus guaranteeing that either the sabino or tobiano allele will be passed on, the same as a homozygous tobiano guarantees to pass one tobiano allele every time he/she is bred. As such, a tobiano/sabino will never be homozygous for tobiano or sabino.

This horse is likely Ee Aa, and certainly nTO nSB1

*Tobiano + Splash
This combination is a little harder to distinguish because both tobiano and splashed white cause nice, round edges. The keys to look for to diagnose a tobiano/splash are missing (or partially missing) chest shield, the bottom-heavy facial markings (since we remember tobiano never causes face white), and overall a smaller amount of white than you'd expect to be caused by tobiano alone.

Below is Pusher's Romper Stomper. He carries tobiano + splash as pattern genes. It is possible but not likely that he carries sabino. The tobiano is clearly evident again due to the dark head, chest, and flanks. The splashed white is subtle, only there if you know where to look. The bottom-heavy face white is a dead giveaway, along with the reduced chest color (compare to the tobianos above), and increased amount of overall white. Also notice how the edges on the spots stay nice and smooth, unlike the jagged edges caused by the presence of sabino.

Davey's genetics likely read Ee aa nTO nSpl

*Tobiano + Frame
Frame is rare in Tennessee Walkers, but it does occur. Tobiano + Frame can be hard to identify because, unlike the other overo genes which even in minimal form will alter tobiano to a recognizable degree, frame can exist with tobiano and still not show a single sign or give a clue. Due to the danger involved with lethal white overo, it is best to test for frame if you believe your horse could carry the gene and you plan on breeding.

Here is an example of a tobiano/frame where both patterns are expressing well. Notice the face white and two solid legs - dead giveaways of another gene at work on the tobiano. You can see the "frame" color working trying to keep the white in jagged patches "framed" on the side of the body while the tobiano tries to keep its usual dark chest, flanks, and head. Also, this horse's topline has only a small amount of white crossing over on the neck - another clash between the frame trying to keep the white off the topline and tobiano trying to do just the opposite.

This horse is likely Ee Aa nTO nO

*Tobiano + Sabino + Splash
To spot a horse with these three genes at work, look for characteristics of each gene. Pusher's Easy Breeze (below) is a wonderful example. You can see right off the tobiano is putting color on the face, flanks, and is trying for color on the chest, too. However, splash has wiped a good bit of the color tobiano wants ON the chest off. Also, the bottom-heavy face white is very characteristic of splash. Sabino is evident in the jagged edges of the spots, and in person this horse has sabino roaning evident.

Easy is Ee aa nTO nSB1 nSpl

III. Dilutions

Everyone loves a horse of a different color. The dilutions are the genes that cause a horse's base color to be - what else - diluted! Three of the most common dilution genes are cream, champagne, and dun, and the addition to one of these genes on a base color can create a shade anywhere from black to extremely pale off-white, or anywhere in between.

A.) Cream. The cream dilution is the most common type of dilution. Cream is the dilution gene responsible for palominos, buckskins, cremellos, perlinos, smoky blacks, and smoky creams. A horse can be either heterozygous (Cr/cr) or homozygous (Cr/Cr) for the cream dilution gene. If a horse is homozygous for cream, they will always produce a cream dilute foal.

    1.) Cream + Chestnut. A chestnut based horse (ee) that is heterozygous for cream 
    will be a palomino. A chestnut based horse that is homozygous for cream will be a cremello. 

This horse, carrying one copy of cream over a chestnut base, is a palomino. The magnitude of cream's dilution on a particular horse varies depending on several factors. Thus two horses of the same genotype can have different phenotypes (physical appearances). This deep golden dappled palomino has a genotype (ignoring the pattern genes) of ee ?? nCr

This palomino has the same genotype as the horse above. He is a pale cream color, similar to cremello. The varying shades cream can cause is the perfect reason you can NOT use the shade of the horse's coat to determine whether it is a single or double dilute cream. This horse is palomino, evidenced by his dark skin and eyes. A double dilute (homozygous) cream will always have pink skin and 2 blue eyes. This horse is ee ?? nCr

A chestnut based horse who is homozygous for cream is a cremello. Cremellos are always pale, and have pink skin and blue eyes. This gorgeous Thoroughbred stallion is a cremello, and his genotype reads ee Aa CrCr


    2.) Cream + Bay. 
    Cream dilutes red much more than black. Thus, a bay horse with a cream gene will maintain its
    dark legs, mane, and tail. A bay horse with two cream genes (homozygous) will be much more 
    pale, but the dark points will still be visible as they will remain darker than the "red" or "brown"
    portion of the bay's body.

This gorgeous Tennessee Walking Horse, Golden Gambler, is a buckskin. He stands at stud in Virginia (click his name for more details) and his genotype reads Ee AA nCr

A homozygous cream (Cr/Cr) horse with a bay base will be a perlino. Like all homozygous creams, perlinos have pink skin and blue eyes. They are easily distinguishable from cremellos since they have the dark lower legs and darker manes and tails. This stunning perlino Walking Horse has a genotype that reads Ee AA CrCr
   The Buck Starts Here 

    3.) Cream + Black.
    The cream dilution on a black based horse causes smoky black and smoky cream. A smoky black
   will often look very similar to a regular black, as cream in heterozygous form does not do much to
   dilute black. However, a smoky cream (homozygous cream on a black base) will be clearly diluted
   although much darker than a cremello or perlino.

This horse is a smoky black. As you can see it looks very similar to a regular black horse. However, smoky blacks will usually have a "sun faded" look as this one does, whether they are truly sun faded or not. This horse's genotype could be Ee aa nCr

This gorgeous pony is a smoky cream. Like all double dilute (homozygous) creams, he has pink skin and blue eyes. However, his coat color is much darker than that of a cremello or perlino. His genotype likely reads Ee aa CrCr

B.) Champagne. The champagne dilution is my personal favorite dilution, and may be me favorite color gene. Like cream, a horse can be homozygous or heterozygous for champagne, and if it carries the gene it will express it. However, unlike cream, the only reliable way to distinguish a homozygous champagne from a heterozygous champagne is to DNA test the horse for the gene - there is no change in skin color, eye color, etc., that indicates whether the horse is carrying one or two copies of the champagne gene.
One characteristic of champagne that makes it easily distinguishable from cream and other dilutions is the skin mottling it causes. Champagnes also often have green eyes, many are born with blue eyes which turn green later. Most champagnes are born dark and lighten with age.

    1.) Champagne + Chestnut. A chestnut horse (ee) with one or two champagne
    genes is called a gold champagne. 

This is a gold champagne at birth. Notice how dark the foal is - he looks chestnut, but the blue-green eyes and skin which will develop mottling give away the fact he is champagne. This little guy's genotype is most likely ee Aa nCh

This is a gold champagne adult. Notice the color is very similar to palomino, but even though this isn't a close-up of the horse's nose/eyes, you can see the skin mottling going on. This horse's genotype is most likely ee aa nCh

This is a homozygous gold champagne adult Tennessee Walking Horse. He is a little but paler than one might expect a heterozygous gold champagne to be, but other than that there are no physical indicators to suggest he is homozygous for champagne. His genotype reads ee aa ChCh


2.) Champagne + Bay. A bay based champagne horse is called an amber champagne.

This is an amber champagne mare and foal. Again notice how dark and non-diluted the foal is at birth, but the eyes and skin give away the presence of champagne. This foal's genotype could be Ee Aa nCh

This is an amber champagne adult Quarter Horse. Notice the similarity between this color and buckskin, yet the skin mottling is clearly evident on this horse. Also notice how champagne dilutes the black point just a little bit more than cream does. His genotype could read Ee AA nCh


  3.) Champagne + Black. A black based horse with champagne is called a classic

This is a classic champagne foal. Again, notice how dark the coat is, but the skin and eyes are clearly evident of a champagne. Ee aa nCh

This is a classic champagne mare and her foal, which looks closer to amber. Notice the champagne "sheen" is evident.

A close up of champagne skin mottling and eyes on a champagne.

4.) Champagne + Brown.  A brown based champagne is known as a sable champagne.

A sable champagne tobiano. Notice that this horse looks very similar to a classic champagne; yet his points are darker than the rest of his body, as is typical of the seal brown color since agouti is at work on it.

   C.) Dun. The dun dilution is fairly rare in Tennessee Walking Horses; indeed, it is most commonly seen in Quarter Horses and mustangs. Unlike the other two dilution genes we have discussed, dun does not add any "gold" or "silver" sheen to the horses it affects - it simply dilutes the base color, leaving the head and legs dark. For example, a chestnut horse carrying dun will have a normal chestnut-colored head and legs, with the body a lighter shade of chestnut. The key characteristic of dun is the dorsal stripe - a dark stripe the color of the horse's undiluted base color running along the top of the horse's back. Dun also sometimes leaves "leg barring" evident - zebra-like stripes on the horse's legs, usually located above the knee and on the hock.

    1.) Dun + Chestnut. This combination is referred to as a "red dun." 

This horse is a red dun. Notice how the dun dilutes the body and leaves the legs. 
ee ?? nD

    2.) Dun + Black. This color combination is what is commonly referred to as "grulla" or "grullo".

A grullo Quarter Horse. Notice the dark head, legs, and extremely evident dorsal stripe.
E? aa nD

    3.) Dun + Bay. This color combination is known as - what else - bay dun!

This is a bay dun Morgan stallion. Notice the bay dun looks more diluted than the other shades of dun, with the body color diluted and points left dark - this horse could be mistaken for a buckskin.
E? A? nD

Example of leg barring on a grullo.

D.) Silver. The silver dilution gene is not too common, but is growing more prominent in Tennessee Walking Horses. The breed most known for this dilution would have to be the Rocky Mountain Horse. Silver dilutes only black pigment, so while a chestnut horse can carry silver, it will not appear diluted. The only way to find out if a chestnut based horse is carrying the silver dilution gene is to test it, or to breed it and see if it produces a silver foal.
Thus, there are only two kinds of silver:

    1.) Silver + Black. Commonly termed silver black. This is a black horse with a silver gene. The most distinguishing features on a silver black are the body color diluted to a chocolate-brown, or sometimes "silvery" shade, and the mane/tail diluted to any shade ranging from silver/gray to pure white.

This is a common expression of silver black. Commonly referred to as "chocolate." E? aa nZ

Another example of a silver black.
E? aa nZ

    2.) Silver Bay. A bay horse + silver. Since the silver dilution only affects black pigment, the horse's body tone will not be affected. The legs will be diluted to a chocolately or silvery color, and the mane and tail will often be diluted much the same as in a silver black.

A stunning silver bay miniature horse.
E? A? nZ

Another stunning silver bay, this one a Kentucky Mountain Horse.
E? A? nZ

    There are other dilutions, however they are so rare I will not even go into them. However, I will put in a quick word on the newly discovered "pearl" dilution gene. It is very unique as it is recessive - meaning the horse must carry two copies of the gene for it to be affected. However, if a horse carries cream and pearl or champagne and pearl, it will be quite light, as with a typical double dilute.

Homozygous pearl:

Smoky Black + pearl

>> Horses carrying more than one type of dilution gene. Of course, horses can very well carry a copy of the cream dilution in addition to a copy of the champagne dilution. It can be increasingly tricky to determine what dilutions a horse is carrying when he/she carries more than one kind. In this section I will do my best to explain ways you can tell which dilutions a horse is carrying when multiple dilutions are present.

*Cream + Champagne
The combination of one or more cream genes with one or more champagne genes is fairly common and very popular in many breeds, not the least of which is the Tennessee Walking Horse. A cream + champagne carrier - known as a cream champagne or a double cream champagne - is characterized by a rather diluted coat (often very similar in shade to the double dilute creams - cremellos, smoky creams and perlinos), as well as the characteristic champagne green eyes and skin mottling.

A chestnut-based horse carrying 1 cream and 1 champagne gene; a.k.a a "gold cream champagne." Notice that this horse is extremely pale, much like a cremello, but has the champagne skin mottling.
ee ?? nCr nCh

A bay horse carrying 1 cream and 1 champagne gene - known as "amber cream champagne." This is our filly, Confederate Girl. She has been tested, and based on testing, her phenotype, and her pedigree, we know that her genotype reads Ee Aa nCr nCh

This horse is an absolutely stunning classic cream champagne Tennessee Walking Horse - a black based horse with 1 cream and 1 champagne gene.
Ee aa nCr nCh

This horse is a sable cream champagne - a brown based horse carrying one cream and one champagne gene. These horses can look very similar to amber cream champagnes (as this one does), or very similar to classic cream champagnes.
E? A? nCr nCh

Double Cream Champagne. This describes a horse which is homozygous for the cream dilution (CrCr), and also carries one copy of the champagne gene. These horses are generally very pale, and much or all of their skin mottling is knocked off, thanks to the 2 copies of cream removing most of the pigment from the skin. They will generally look like cremellos, but are usually even paler (approaching nearly pure white), and often will still exhibit the champagne "sheen" to their coats, as this horse, a Tennessee Walking Horse stallion, does.
ee ?? CrCr nCh

*Note: I am 100% confident that a homozygous champagne horse carrying a cream gene can and does exist. Unfortunately, I have not been able to find an example nor any info on the color. Therefore, I am leaving this color out. If you know anything about this color, or have seen/heard of a horse of this color, please let me know - I would very much appreciate it!

*Cream + Dun

All right, this is the stage where some of your former knowledge is going to come into play! No longer will I be mentioning the base color of the horse - you should know that by now! For example...

is a palomino who also carries dun (hopefully you were able to figure out based on the "palomino" part that this horse is red based - ee!)

Check it out - this horse looks a lot like a palomino but that dorsal stripe is evident!
ee ?? nSB1 nCr nD

is a buckskin who carries a dun gene. (Bay + cream + dun - are you getting the hang of it now?)

This horse looks buckskin, but once you notice all that leg barring, can't you just tell he carries dun? He is definitely a dunskin!
E? A? nCr nD

Smoky Grullo
Well, what else would this be except a smoky black + dun!

This horse is a stunning example of a smoky grullo. He looks a touch more diluted than a regular grullo or smoky black - his body almost appears to be the shade of a classic champagne. The leg barring is again a clear indicator of dun!
E? aa nCr nD

IV. Other Modifying Genes

Separate from the dilution genes and pattern genes, these modifying genes change a horse's base coat color, usually without diluting it or breaking it up as the "pinto" genes do.

A.) Roan. One may call their horse a roan if and only if it carries the true roan gene! Roan is characterized by white hairs scattered through the horse's coat on its neck and body; the head and legs remain the base color with no roaning. Other genes - namely, SB1 (sabino) and rabicano (which we will discuss later) are well known to cause roaning; however, horses carrying these genes are NOT technically roans.

    1.) Black Roan. The common slang term for this color is "blue" roan. This is a black horse with at least one copy of the roan gene.

This is a beautiful "Blue" roan Tennessee Walking Horse name Neon Blue.
E/ aa nRn

    2.) Bay Roan. This is, what else, a bay horse with at least one copy of the roan gene.

A bay roan foal. This is the most striking roan color, in my opinion.
E? A? nRn

    3.) Chestnut Roan. A chestnut based horse carrying at least one copy of the roan gene. Commonly termed "strawberry" or "red" roan.

Here is a chestnut roan mare. Notice the dark legs and head.
ee ?? nRn

distinguishing between sabino roan and true roan...

This Tennessee Walking Horse mare, Jazz's Precious, is a chestnut sabino with a ton of sabino roaning. Yet, notice that her head (and legs) are also roaned, and her mane and tail are lighter than the real chestnut roan pictured above. 

B. Grey. Grey is a modifier which works by gradually turning every hair on the horse's body white. Grey affects each base color just the same, so for this section we will just go over what changes in phenotype a grey horse typically goes through in its lifetime.

    1.) Birth. A grey horse at birth is born its base color, and often has tell-tale grey "goggles" around its eyes or a funky shade on its legs or muzzle which indicates it will go grey. 

This bay foal has very obvious grey "goggles" around his eyes. It is a safe bet he will grey out as he ages. 

    2.) Youth (up to about 4-6 years). The rate at which grey turns the base color white varies from horse to horse. Typically, a young horse will gradually lose its base color for gorgeous grey dapples. This is what a young horse will look like as it begins to grey.

Notice that on the horses above, who are each probably not more than 2 years old, much of their base colors are still quite evident.

Above: another young horse, I'd venture to guess about 2-3 years old, going grey.

Above: This horse has all but turned completely grey; this is the gorgeous dapple phase that many greys go through. This horse is probably between 4-5 years old.

Above: These two horses are beginning to turn white in some areas. This stage of grey typically occurs at about 5-6 years.

    3.) Aged Horses. For this category we will consider horses aged 7 and up to be "aged" and thus in the final stages of "greying out." This is where the horse loses those gorgeous dapples for a white coat.

A stunning grey Arabian, probably approaching her 10th birthday.

Another gorgeous grey; this guy is probably into his teens. Notice that the legs tend to be the last to be affected.

The final stages of grey - the end result. 

Note that when a horse carries the grey modifier, every hair will eventually be turned white. This means that grey has the power to "erase" white markings - tobiano spots, stockings, stars, appaloosa spots, and everything else. A grey palomino tobiano and a grey with a simple chestnut base will wind up looking exactly the same by the time they are 20 or so.

C. Sooty/Smutty. This is a particularly neat modifying gene. The sooty gene is characterized by a darkening of pigment in certain areas - typically along the topline and on the horse's legs - and often causing dappling. 

A sooty buckskin.
Sooty / Smutty Horse

A pair of particularly stunning sooty palominos:

Notice how sooty can affect the mane/tail color as well.

A strikingly pretty sooty palomino Tennessee Walker mare. This horse is a full-sister to a mare we used to own, Shoot Yeah.

        >Brindle. The inheritable form of brindle is believed to be caused by a mutation of the sooty gene. Brindle is an extremely rare coat color/pattern that very little is known about; I simply wanted to add it here since it is somewhat linked to the sooty gene.

Here is our brindle Tennessee Walking Horse filly, Cajun Belle. We don't know whether she has the inheritable form of brindle or not (the one believed to be caused by a mutation of the sooty modifier). As a black horse, it is fairly hard to notice the brindle in the picture below, but you can see it if you look close:

It comes out much better when she is sun bleached just a little: