In equine color genetics, grey and roan are considered to be what type of genes?

In equine color genetics, grey and roan coats are classified as modifying genes because they influence the expression of other base coat colors without being tied to a specific pigment themselves. The grey gene, for example, causes a horse's coat to lighten progressively with age, affecting the base color. The roan gene, similarly, modifies the base color of the horse by intermingling white hairs with the original coat color, creating a distinct look.

Understanding these genes as modifiers highlights their role in how they interact with other coat color genes rather than as standalone colors. This interplay can lead to a variety of appearances within the same base color family based on the presence of these modifying genes. This distinction is crucial in equine genetics, as it helps breeders and evaluators predict how specific traits may manifest in offspring, allowing for informed decisions in breeding practices.