Chestnut is a hair coat color of horses consisting of a reddish-to-brown coat with a mane and tail the same or lighter in color than the coat. Genetically and visually, chestnut is characterized by the absolute absence of true black hairs. It is one of the most common horse coat colors, seen in almost every breed of horse.
Chestnut is a very common coat color but the wide range of shades can cause confusion. The lightest chestnuts may be mistaken for palominos, while the darkest shades can be so dark as to resemble a black coat. Chestnuts have dark brown eyes, black skin, and a coat that is entirely devoid of true black hair. Typical chestnuts are some shade of red or reddish brown. The mane, tail, and legs may be lighter or darker than the body coat, but are never truly black. They may have pink skin beneath any white markings under the areas of white hair, and if such white markings include one or both eyes, the eyes may be blue.
Chestnut is produced by a recessive gene. Unlike many coat colors, chestnut can be true-breeding; that is, the mating between two chestnuts will produce chestnut offspring every time. If any color other than chestnut occurs, one of the parents was not chestnut. Some breeds, such as the Budyonny, Suffolk Punch, and Haflinger are exclusively chestnut. Other breeds, such as the Belgian are predominantly chestnut. However, a chestnut horse need not have two chestnut parents. For example, Friesian horses have been selected for many years to be uniformly black, but on rare occasions chestnuts are born. The Ariegeois pony is another example.