Groundhog fur has two parts to it. They have an undercoat that is very dense, and that is gray in color. They also have a longer outer coat that can be a variety of shades of brown and even blond.

The color of the outer coat is how I can tell some of Mabel's remaining pups apart. Two are dark brown that could be mistaken for dark grey, one is reddish, and one is a blond. Of course, when they're shedding coat, then, I must rely more on other physical traits to tell who is who. Although the now grown pups each must have their own burrows elsewhere, all seem to return to their maternal first home. So, I see different individuals on different days.