Equine coat coloring is controlled by numerous genes acting in combination to produce a multitude of variations in pigmentation.
These genes, which are inherited are located on paired structures known as chromosomes; the modern horse has 64 chromosomes, half of which are inherited from the sire,
the other half from the dam. Some genes are dominant, others are recessive. For example, in horses, chestnut is recessive, all other colors, bay is dominant to black.
The dominant greying gene can result in horses which are born with a dark coat turning progressively more grey as they grow older. This is especially noticeable in the Lipizanner,
whose foals are born dark and, with rare exceptions, turn grey as they mature.
Coat color and markings developed over millions of years to give the horse the best camouflage possible for the area the horse lived. The most primitive horse and pony color is Dun (yellowy beige) with black points (points being mane, forelock, tail, and lower legs). Old stories tell of "good" and "bad" colors in horses. Chestnut horses were supposedly hot tempered, black as being nasty and lacking stamina, bay and brown dependable, and so on. The truth is that color has no bearing whatsoever on temperment or performance ability.
The only exception to this are horses who have pink skin under white hair (some white haired horses have dark skin underneath). These horses are much more susceptible to weather than others, because pink skin lacks the strengthening substance melanin which is responsible for skin and hair color. The pink hue comes from blood circulating through the colorless skin. Because the skin is less resistant to sun and wet, and hence bacteria, it becomes more easily infected with skin diseases, sunburn, and allergies.
True Albinos have no coloring agents in their bodies. They have pink skin, white hair, and pink eyes. Some so-called albinos have blue eyes, but this is not true albinism, as blue is a coloring matter. Blue eyes are not all that common in horses, however, and where it does occur often only one eye is blue, called a wall eye. There is no evidence that wall eyes see less well than dark eyes, but albinos with pink eyes (due to blood circulating through the iris) are known to have poorer sight.
The following are some basic colors of the horse:
(varying from reddish to yellowish) That always has a black mane, tail, and black legs, referred to as points.
CHESTNUT or SORREL :
A chestnut horse is a horse whose coat is basically red. Varies from a pale golden color to a rich, red gold. The mane and tail are normally the same color as the body, but may be lighter or darker than the body. If the mane and tail are lighter in color than the body, the horse is referred to as having a flaxen mane and tail. Thoroughbreds of this color are called chestnut; quarter horses are called sorrel. The darkest of chestnut shades is referred to as a "Liver Chestnut" and usually has a flaxen mane and tail.
Dark brown or nearly black. If ANY brown hairs are visible on the face or body, the horse is brown rather than black. Many brown horses are mistakenly called black. But a close examination of the hair around the muzzle and lips will soon confirm if the horse is truly black or brown.
All hairs are black, although white markings may be found on the face and lower legs. A black horse has black eyes, hooves, and skin. If there are tan or brown hairs on the muzzle or flank, this horse would be referred to as a seal brown
Yellowish or tan with similarly colored mane, tail, and legs. A Dun has a dark "Dorsal" stripe running down the back.
Same as dun, but legs, mane, and tail are black. A Buckskin may or may not have the dorsal strip running down the back.
Golden, with flaxen or whitish mane and tail.
A mixture of black and white hairs throughout. The coat varies from light to iron (very dark). The skin is black. A "Fleabitten Grey" coat is flecked with brown specks. A "Dappled Grey" has a light grey base coat with dark grey rings.
Most so-called white horses are gray. The only true white horse is an albino. If the horse at any time of its life has had hairs of any color other than white, it is probably a gray.
Black or brown with a sprinkling of white hairs (blue roan), or chestnut with a sprinkling of white (strawberry roan).
More or less circular patches of hair in a different color than the base coat. Distributed over the body in various sizes and amounts.