someone correct me if im wrong but a kole tang is a kole tang . Some just have juvenille coloration(light blue, or blue spotted) and then at maturity they go deeper purple with yellow eyes.
as far as them i have one, he is a VORACIOUS algae eater, def. a good pick he keeps the tank very well maintained !! not aggressive at all, very quick!
mine actually doesnt eat flake dfood, or pellets or anythign. Just a;age off my rocks and glass