Which color describes a horse with a true black mane, tail, and coat?

A horse that has a true black mane, tail, and coat is classified as black. This color is characterized by a uniformly dark coat without any lighter areas or markings and is the true representation of the black color in horses. When identifying horse colors, the specific characteristics of the mane, tail, and body coat are crucial. In this case, the consistent black coloring across all these areas clearly defines the horse as black.

Other options represent different colors: buckskin is a tan color with a black mane and tail, gray refers to a color that changes from black or dark to white as the horse ages, and chestnut is a reddish-brown color that is distinct from the black designation. These color distinctions help in understanding the genetics and breeding standards in horses.