Board Thread:Questions and Answers/@comment-24366751-20170226040817/@comment-24922135-20170226173413

Ben being black would not change the colours of his aliens, however I do believe that the omnitrix contains DNA of the different races of each species (after all, the omnitrix was made to end racism). Therefore there are only two (iirc) species canon to Ben 10 that have different races, those being:
 * Necrofriggians (race varying by planet of origin)
 * Humans (this one is self explanatory, but not an idea that CN would ever entertain unless you counted Osmosians)