Both fox squirrels and gray squirrels can come in black. In fact Linnaeus named the fox squirrel Sciurus niger because the one he worked on was a black one. Black phase gray squirrels (Sciurus sciurus) are common here in Michigan. Black phase fox squirrels pretty uncommon around here. The two species can interbreed by the way, which can make for some interesting patterns, like fox squirrel color with a black tail, for example.