Eye pigment is unrelated to leucism. An animal can still be a true leucistic and have colored eye pigment, as the defect causing leucism is rooted solely in the skin of the animal. This would explain why no matter what you mix with a leucistic, it always lacks color--melanin or pigment cells of any sort die in the skin as a result of the defect. Super Lessers and Butters are true leucistics, while Super Fires and Mojaves aren't, as their skin can clearly support even trace amounts of pigment. By the standards of this paper, the classic yellow-blotched look of Super Fires/Sulfurs might actually be a form of Piebaldism, but you'd have to see if normal pigment could be sustained by the white patches of skin to prove or disprove this I suppose.
Cheers,
-Matt