Honestly, looking at his thumb, the tip looks white but the base looks black. There's a line, almost like he was burned or bleached or something. I've seen lines in skin like that before where something happened and made part of the skin way whiter than the rest of the skin. I don't think it really proves anything.
Furthermore, despite what Enzom might tell you, a person is who they are, not what they look like. And just writing this post investigating his skin color makes me feel icky inside. Enzom being white or black doesn't change the fact that he's an insufferable twat.