Hi! Where did you get it and did you buy it as a Cornish Cross? I've never had one with black like that, but maybe it happens. If it's in with other Cornish Cross, you can compare it size-wise (especially the legs!).
Did you post somewhere else that you got this at TSC? It makes me wonder if they mixed up a few "Tetra Tints" and Cornish Cross when they were putting them in the bins. They look pretty similar as day olds.