the dun gene. Red dun, also called claybank, is a light tan coat with reddish instead of black points and primitive markings. Genetically, the horse has an underlying chestnut coat color, acted upon by the dun gene. Thus, as there is no black on the horse to be affected, the undiluted underlying color is red. Grullo or grulla, also called blue dun or mouse dun, is a smoky, blue-gray to mouse-brown color and can vary from light to dark. They consistently have black points and they often have a dark or black head. The primitive markings are usually all black. Genetically, the horse has an underlying black coat color, acted upon by the dun gene. Another characteristic of the dun gene are primitive markings. Dun traits include the following: Dorsal stripe down the center of the back, along the spine, seen almost universally on duns Horizontal striping on the back of forelegs, common on most duns, although at times, rather faint Facial mask, a darker area around the nasal bone and forehead, sometimes making the head close to the undiluted color, some patterns colloquially called "Cobwebbing." Transverse stripe, a crosswise stripe along the shoulders perpendicular to the dorsal stripe, very common in donkeys, less common in horses, and if present, often faint, usually only visible on a short summer coat, if at all. Frosting: light hairs found on either side of the mane and on both sides of the dock of the tail. Other variations result from the interplay of additional genes: Chestnut + dun + cream gene (single copy) = "dunalino" or "palomino dun" Bay + dun + cream gene (single copy) = "dunskin" or "buckskin dun" A single copy of the cream gene on a black base coat does not significantly lighten black hair, though it may have a subtle effect, and thus a single copy generally has no visible effect on a grullo, either. Conversely, double copies of the cream gene create very light-colored horses (cremello, perlino, and smoky cream). Thus, if a horse with two cream dilution alleles also carries the dun gene, it also will be cream-colored, with primitive markings not visible to any significant degree. Dorsal striping alone does not guarantee the horse carries the dun gene. There two types of non-dun, called non-dun1 and non-dun2. Non-dun1 horses have no dun color dilution, but may keep primitive markings, while non-dun2 horses have neither the