I am almost certain it is a black. I have kept all three species and it looks almost identical to black bullheads. Browns almost always have some sort of pattern, blacks usually don't. Yellows always have the white lower whiskers, others do not. And just from the general look of it compared to browns, I say black.
LOL, it looks like the only way you're going to be able to know FOR SURE is to wait until he is larger.
It's a half and half thing (With some saying Yellow) between Brown or Black.