colors

Basic Equine Color Genetics

Dominant genes mask the presence of their corresponding recessive gene.
Therefore, a horse of a dominant color must have one parent who carries the gene for that color. This does not necessarily mean, however, that they must have a parent who is that color (ie, if you breed a black horse to a chestnut, you may get a bay foal, because the black parent donated the dominant gene for black points, but the chestnut one donated a dominant bay body color gene, as well as the recessive red point color gene)
Genes are inherited in pairs, one from each parent. A horse with two identical copies of a gene is known as homozygous for that trait, while a horse with two different versions is called heterozygous.

basic coat colors
The basic body colors are black & chestnut, with black being dominant over chestnut.

Via a seperate dominant gene, the black can be restricted to the horse's points (mane, tail, & legs), creating a bay.

dominant modifier genes-a horse may show more than one of these colors.
The Smutty gene is dominant. It causes an 'overspray' of black on the horse's body, turning bay to dark bay, chestnut to liver chestnut, palomino to smutty palomino, etc. It is believed that seal brown is caused by at least one other modifier gene in combination with the Smutty gene.

Roan is dominant and may appear on top of any body color. A true roan horse (as opposed to one that is greying out) will normally have a darker face, with the roaning ending about where the neck & head join, as well as dark points.

Grey is dominant and progresses as the horse ages, often showing first on the face.

Rabicano, white at the top hairs of the tail (think the Quarter Horse Go Man Go's coon tail), often also causing light roaning on the flanks, is dominant.

dilution genes-more than one of these colors may be present on a horse.
Dun is dominant and always lightens the body color (causing grulla, dun, creamy dun, muddy dun, red dun, or apricot dun), as well as producing a dorsal stripe and sometimes leg bars and spiderwebbing.

Champagne is also a dominant dilution. Genetically bay or chestnut horses with this gene tend to be mistaken for buckskins or palominos, but the champagne gene also causes dilution of a black horse's color, similar to how the dun gene would act. The best way to tell if a horse is champagne is that he will have pink skin with a few black mottles/spots and amber or blue eyes. The site www.champagnehorses.net has lots of information on this gene.

The Silver Dapple gene is rare, occuring in only a few breeds, including the Dutch Warmblood, Shetland Pony, Morgan, and most commonly the Rocky Mountain Horse. It is dominant; and that famous Rocky color of flaxen chocolate is what it often produces. It acts only on the black areas of the horse, turning the mane & tail flaxen, and often lightening the leg color. On an entirely black horse, it will also turn the body color to a lovely dappled chocolate shade. Chestnut horses can carry this gene, but will not show any color change. Confusingly, this gene can make a bay horse appear to be a flaxen chestnut; one reason why it was only recently recognized to exist in the Morgan breed.

Palomino & buckskin are caused by the same dilution gene, known as Creme. It is not dominant or recessive, but rather classified as 'incompletely dominant,' which means the affected traits mix. In this case, the gene causes the brown areas of the horse to dilute, like mixing with white paint. When a horse has one Creme gene, it turns from a bay to a buckskin or from a chestnut to a palomino. A black horse may carry one creme gene with it showing just a hint of dilution, or sometimes it dilutes almost to liver chestnut; either way this is called a smoky black. When a horse receives a creme gene from each of its parents, however, its color is diluted all the way to a creamy white, known as perlino (if the horse is genetically bay), cremello (if the horse was chestnut), or silver smoky (if the horse was black; this may have a bit darker cast than the other two). The way this gene works makes the only sure way to get a palomino foal, to breed a chestnut horse to a cremello.

recessive point color genes
A recessive gene causes a chestnut horse's points to go flaxen, creating a chestnut ruano.

A recessive gene also rarely causes a horse's black areas to be a dark brown instead, known as chocolate chestnut. Though this horse would genetically be black, it is a shade of brown visually, and so is commonly classified as a shade of chestnut. Therefore, a bay horse with this gene, since it is visually chestnut with darker points, is called a chestnut tostado.

white markings-a combination may be present
White leg & face markings have a tendency to resemble those of the horse's parents.

The Sabino pattern of white tends to expand through generations, becoming more extreme in certain lines until it grows into a certifiable pinto pattern, so it can be loosely classified as dominant in the sense that two horses with no white markings are probably not going to produce a sabino. It is generally expressed as high stockings (think Clydesdales), but may expand over the face too, which is why it is sometimes confused with the overo pinto pattern. The markings have roan-y, blended edges, and when very extreme may produce an almost entirely white horse (this is where 'white' Thoroughbreds come from; see www.goldhopefarm.com for more information). May be confused with tovero.

Splash White is dominant, but linked to a hearing-impairment gene. Splash White is similar to sabino in that it causes markings to extend from the head & legs toward the body, but the edges are crisp like a tobiano instead of roaned. May be confused with tovero.

Frame overo is dominant. Overos tend to have at least one colored leg, unusual white markings on their heads, a horizontally-oriented pattern of white, blended or roan-y edges to their markings, one-color tails, and often white does not cross their spine. Be warned, though, that breeding two frame overos together will, 25% of the time, result in a foal with Lethal White Syndrome, in which it is born completely white and with a nerveless intestinal tract, shortly causing death.

Tobiano pinto is caused by a dominant gene. Tobianos tend to have four white feet, normally-marked heads, a vertically-oriented white pattern, clean edges between white & color areas, colored flanks, white crossing the back at some point, and may have two-colored tails.

A horse with both tobiano & overo characteristics likely has the genes for both patterns & is called tovero.

Appaloosa markings are not well understood; at this point each pattern (leopard, few-spot leopard, white blanket, spotted blanket, snowflake, and varnish roan) is generally considered to be dominant, and a horse may not uncommonly display more than one pattern and also become more white as it ages. Few-spots and "snowcap" blankets are currently thought to be expressions of homozygosity for leopard and blanket patterns, respectively, since they are observed to throw 100% color.

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