Though both chestnut and sorrel refer to the same general tone of reddish-brown (or brownish-red), the colors are slightly different from each other and possess a few unique characteristics that do not overlap.
Basically, a Sorrel horse has a completely red base coat color (aside from the possibility of white markings), and a Chestnut horse’s coat color can be any shade of red, including almost brown or ‘liver’ chestnut.
A sorrel horse , have a flaxen colored mane and tail, but if there are black markings anywhere on his body, that horse would then be considered chestnut.
Chestnut is often described simply as “red”, often takes on a darker sheen, or can even look wine-colored.