Instructions
Consider that grulla is actually the dun gene working on a black base color. The horse's genetic color is black, but it is paired with the dun gene, which will lighten it and cause the mane and tail, as well as the face and legs, to display the darker base coat color.
Keep in mind that different shades of grulla are called different things. The lightest shade of black dun is called "Silver Grullo," then comes "Slate Grullo," then "Grullo," then "Lobo dun," with this last being the darkest shade in the grulla coat pattern.
Look for a mousy-gray, smoky-blue or slate-gray color on the body of the horse. The black base coat color is diluted by the dun gene to an off-black, bluish, smoky-gray color; in some cases, the horses are more mousy-brown-tan. It is almost a "nougat" color, like you find inside a candy bar.
Look for the defining dun characteristics. The dorsal stripe will be there and is black, and the face and legs are often darker than the body.
How to Identify the Grulla Color in a Horse
Horses come in all shapes, sizes and colors. The grulla color is one of the rarer coat colors. Pronounced "Grew-Yuh," it is the Spanish word for the blue-gray crane. The coat of the horse is often described as a mousy-gray, smoky-blue or slate-gray color. The grulla color is very striking, and though it is hard to define, once you see it, you can easily identify it again.