1) Horse coat color 
Grullo 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 i...
American term to describe a mouse dun coat colour.
A type of dun with a smoky or mouse-colored body, and usually having a black mane, tail, lower legs, and dorsal stripe