Oh, sorry, maybe I misunderstood.
Well, anyway, Kotal Kahn seems to be based on Huitzilopochtli (already said that on other thread), who is the War/Sun/Sacrifice god of the Aztecs, functions that match exactly on his variations. Even though he has a Quetzal's head as his helmet, feathers and snakes (which resembles another god, Quetzalcoatl, known as "the feathered serpent"), it's more likely he is Huitzilopochtli.
And here is Huitzilopochtli:
And his skin is green on almost all the representations. Quetzalcoatl the same, when on his human form.