Equine coat colors

Horses exhibit a diverse array of coat colors and distinctive markings. A specialized vocabulary has evolved to describe them.

While most horses remain the same color throughout life, a few, over the course of several years, will develop a different coat color from that with which they were born. Most white markings are present at birth, and the underlying skin color of a horse does not change, absent disease.

The basic outline of equine coat color genetics has largely been resolved, and DNA tests to determine the likelihood that a horse will have offspring of a given color have been developed for some colors. Discussion, research, and even controversy continues about some of the details, particularly those surrounding spotting patterns, color sub-shades such as "sooty" or "flaxen", and markings.

Genetically, all horses start out as either chestnut, called "red" by geneticists, represented by the absence of the extension gene ("e"); or black based on the presence of the extension gene ("E"). Therefore, red ("ee") and black ("EE" or "Ee") are the two base colors. The Bay color is expressed when a common genetic modifier, the Agouti gene, works on black. The vast range of all other coat colors are created by additional genes' action upon one of these three coat colors.

Statistically, the most commonly seen horse color phenotypes are identified by the following terms:

White markings are present at birth and unique to each horse, making them useful in identifying individual animals. Markings usually have pink skin underneath them, though some faint markings may not, and white hairs may extend past the area of underlying pink skin. Though markings that overlie dark skin may appear to change, the underlying skin color and hair growing from pink skin will not. Horses may also be uniquely identified by an unusual eye color, whorls, and chestnuts.

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