Colby is a Cervidae stallion with black fur, red eyes, red spots near his hind legs, and silver spines, mane, and hooves.
Colby is Arietem's older brother. He, just like his master Joshua, is very mean and arrogant. He is incredibly self-centered and only thinks of himself, and occasionally his master. Arietem strongly dislikes him, though, just like how Alex does with his older brother, Arietem just tries to put up with him and moves on.