If you're doing something relatively like Homestuck with the alien factor you could use different species of aliens with certain physical traits. Like their physical traits being beneficial but if they were all forced onto a new planet together with different species for one reason or another certain races could claim superiority due to traits or abilities. A number of those different traits could be stuff like gills, horns, certain markings on the skin for camouflage, markings to ward off predators, venom or being poisonous, fins, phosphorescent or luminescent skin, supernatural abilities, as well as things like their bodies being slim and built for speed like a cheetah, or bulky built for strength like a wilder beast, or even really tall or lightweight to help with flying or getting to high areas. Just make them perfect for a certain habitat then strand them on a planet where it's completely different with many other strange people.
I'd go with something like big blotches of certain colors on the skin. Or the absence or presence of certain extra things like extra eyes or fingers, maybe they all have wings and the number of wings on a person describes their status like how most Archangels (like gods hand picked) have three wings or golden ones. Or possibly like a previously stated albinism but for a multitude of colors rather than just albino.
Sorry this is so long, hahaha... I just got really carried away by the ideas. I get really into traits of species and genetic anomalies.