There are two basic coat colors in the equine animal, either black base or chestnut base.
All horse colors are built on a black or a chestnut base and different colors are achieved by dilution genes and color modifiers to provide the wide variety of colors and patterns in existence today. A Few Chestnut Facts
Chestnut horses have no black hairs, they have a red coat and red points
Chestnut and sorrel are interchangable terms and the same genetically
Colors range from dark reddish brown, to deep red to light red
Mane and tail can achieve a sunstreaked look making it lighter than the body hairs
Mane and tail can be almost black all the way to blonde and flaxen