The horse has some of the most varied coat color markings and patterns of any domestic species. Even within breeds, there are dozens of color combinations a foal can develop. It can appear complex, but scientists have pinpointed many of the key elements that make these variations and can actually predict the color and markings of foals.

Annette McCoy, DVM, MS, PhD, Dipl. ACVS, one of the equine surgeons at the University of Illinois Veterinary Teaching Hospital in Urbana, says that horse coloration is a great example of something called “simple inheritance.” This means that a phenotype, or the characteristic we see (in this case color), is determined by a single gene. Each parent donates either a dominant or a recessive version of the trait, and the offspring exhibits the dominant version, unless both parents donate a recessive copy of the gene, in which case the foal will show the recessive trait.

Black or Red, and…

“Coat color is controlled by two base pigments: red and black,” explains McCoy. “Black is dominant and red is recessive.”

So where do all the variations come from? The reason we see so much variety in coat color is that accompanying modifier genes interact with each other and depict what shade and where the red or black will be distributed