What col er is a black hole?

A black hole is colorless. In order for something to have "color," it has to be hit by photons and fly back to the observer. Black holes trap photons within, where they are they are unable to be absorbed and reflect color. It's impossible to know what black holes really look like with our current understanding of the universe but one could assume the singularity itself is a dark grey because it's most likely made of iron.