Actually, I'd have to say it needs to be a two-dimensional idea: It needs to have selection of pre-set styles or colors, and then allow custom colors using the RGB sliders so you can be pleased if you want to immerse yourself or if you just want to go hurt something.
Then I'd say it needs three levels:
1: The "non-choice presets" like Dunmer eyes, Orc eyes, Argonian eyes, Khajiit eyes, (if they go back with the old style) Bosmer eyes
2: Multiple color presets for those races that even have a chance of multiple eye colors
3: Then maybe adjustable palettes, if they don't mind the half of the races covered by option 2 having flourescent day-glo green eyes and such.
Of course with noticing that only half the races (or so) have color options anyway (Unless, of course, they change something up which has happened before), I begin to wonder why they'd bother with anything other than more preset color options. :shrug: