Many black horses "sun bleach" with exposure to the elements and sweat, and therefore their coats may lose some of their rich black character and may even resemble bay or seal brown, though examination of the color of hair around the eyes, muzzle and genitals will determine color.

When identifying the base color of a horse, it is important to disregard all pink-skinned white markings.

White markings and patterns such as pinto and leopard have no bearing on the underlying base coat color of the animal.

When a black horse is sun-bleached, the mane and tail often sun bleach most prominently, and the rest of the coat may have a rusty tinge.

The functional, dominant allele of the extension gene (labeled "E") enables the horse to produce black pigment in the hair.

Without this gene (homozygous recessive condition "ee"), the coat is devoid of black pigment and the horse is some shade of red.

The functional, dominant allele (or alleles) of the agouti gene (labeled "A") enable the horse to restrict black pigment to certain parts of the coat, notably the legs, mane and tail, allowing the underlying red to show through, resulting in bay coloring.

Together, they can determine that a horse that appears visually black is not actually a dark bay or liver chestnut.

Nonetheless, certain individual pairings with appropriate DNA testing can, in some cases, be guaranteed to produce black.