Some horses will completely change there base coat and it will either be pure white or flea-bitten gray. The flea-bitten coat is best described as white hairs with small freckles of red-colored hairs. The red freckles can vary with each horse, some more freckled than others. just like with humans some people have tons of freckles while others only have a few. Most flea-bitten gray horses will be pure white for some period of there life as they make the change to flea-bitten gray.