Wiktionary
n. a colouring of horses characterized by smoky or mouse-colored hairs on the body, often with shoulder and dorsal stripes and black barring on the lower legs
Wikipedia
Grullo or grulla is a color of horses in the dun family, characterized by tan-gray or mouse-colored hairs on the body, often with shoulder and dorsal stripes and black barring on the lower legs. In this coloration, each individual hair is mouse-colored, unlike a roan, which is composed of a mixture of dark and light hairs. The several shades of grullo are informally referred to with a variety of terms, including black dun, blue dun, slate grullo, silver grullo, silver dun, or lobo dun. In the Icelandic horse, the grullo color is called gray dun, in the Highland pony it is called mouse dun, and in the Norwegian Fjord horse, grå or gråblakk (literally, "gray dun").
The word "grullo" originates from the Spanish word grulla, which refers to a slate-gray crane. Because of the origin of the name, some people will refer to a mare as a grulla and a stallion or gelding as a grullo, pronounced and , respectively. (The original Spanish noun is pronounced in American Spanish and in Peninsular Spanish.)
In terms of equine coat color genetics, all of these shades are based on the dun gene acting as a dilution gene over the black gene. Because the grullo color is not due to the gray gene, a grullo horse remains the same basic color from birth, though some minor shade variation may occur from summer to winter coats. If a grullo also carries the gray gene, it will be born a mouse tan-gray shade, but then lighten and eventually develop a white hair coat with age. Because black is less common in general than bay or chestnut, grullo is likewise less common than red duns or bay (classic or zebra) duns. For example, only 0.7% of quarter horses registered each year with the AQHA are grullo.
The most obvious ways to tell a grullo are not only the existence of gray or tan-gray body color, but also its primitive markings, which include some or all of the following: dark face, cobwebbing around the eyes and forehead, dark mottling on the body, leg barring (sometimes called tiger striping), dark ear tips and edging, dark ear barring, dark shadowing of the neck, dark dorsal and transverse striping, and dark mane and tail guard hairs.
Usage examples of "grullo".
That evening when Antonio and the gerente came up to the trap to inspect the horses he was teaching the grullo to back with Rawlins in the saddle.
He led the grullo through and closed the gate and ordered them off the horse and gestured toward the stable with the pistol.
The other two horses went trotting and the grullo started to run along the fence.
In the road he got Junior and the grullo horse looseherded in front of him and with the Blevins horse on the leadrope behind they set out back toward Encantada at a trot.
He didnt know if the grullo horse would try and quit them or not and he wished he had the spare saddle on junior instead but there was nothing to be done about it.
Volpes riding point, mounted on a close-coupled grullo that bore the Snake-Eyes brand on its rump.
Bustamante rode his grullo gelding up to the cabin with obvious pain twisting his face.
The string of spare horses included a mouse-colored grullo whose looks Ennis liked.