Horse Color Genetics:
​The Special Color Genes Overview

​The Special Color Genes
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Most of the horse colors other than red, bay or black are the result of one of the three Base Colors being acted on (altered) by a Special Color Gene. There are three things to understand about Special Color Genes:
  1. Special Color Genes are usually simple genes which work largely as ON-OFF switches. Each horse receives one of two versions of each of these genes: the one that tells them to turn this special color ON, or the one that tells them to leave this special color OFF. If they receive the OFF version, then this gene is not activated at all and has no effect on the horse. If they receive the ON version, then the horse's base color will be altered in whatever way that particular Special Color Gene alters base colors. 
  2. The ON version of the Special Color genes is always the dominant one. If a horse receives even one ON version, the special color will be activated in that horse. 
  3. Most Special Color Genes can be thought of as dominant to the base colors. They replace the base color with something else. (Actually, they alter the base color in a specific way, but the effect is the same as if they replaced it.) If your horse has even one ON version of a Special Color Gene, it will override the base color. 

(Most horses receive the OFF version of all or most of the Special Color Genes. Any horse that is red, bay or black can be assumed to have received two OFF versions for all of its special color genes.)

On the next page, we will look at specific special color genes.