Roan

Roaning is characterized by a mixing of white and colored hairs over the horse’s body, particularly the neck, shoulder, barrel and quarter, while the mane, tail, head, and legs remain solid. The overall effect is that of a lightened appearance to the affected part of the coat. It should never make the coat pure white and will never be completely desaturated. 

Roan may have spots left untouched by the lighter hair, scattered across the coat, called 'corn spots'.

Roan may extend into the mane and show at the base of the tail, similar to dun frosting.

The geno code for Roan is written as:
nRn or RnRn

Roan Range and Corn Spot Minimum and Maximum Size