Originally Posted by Poseidon
Crimson's got the basic idea. A lot of "brindles" are actually heavily marked duns or have strange countershading.
Rainrot and other skin diseases can change the coat different colors. There was a horse posted on here before that was gray, I believe, and then got some kind of skin fungus that made it look all kinds of strange.
Well if youve ever seen any horses that inherit both genes of HERDA the scarring usually looks pretty strange if they heal
Obviously in most cases those horses are euthanized before the age of 5