>>29722859i've done this in my fire red romhack (see lunatone sprite sheet here for example)
as you can see, 8 different colours. some are rarer than others however, and your chance of encountering each colour wild varies
in order, left to right:
abundant ("normal" colour)
common (1/4)
uncommon (1/16)
rare (1/64)
elite (1/256)
exotic (1/1024)
shining (1/4,096) standard shiny chance basically
mythical (1/16,384) for laughs
as you can see, its colour scheme gets more and more outlandish as it gets rarer. its two rarest schemes are the only forms that show the "sparkle" effect when they're seen as it'd get really annoying if just over a quarter of all pokemon you see in battle sparkle.
are people really interested in this? i might clean my code up for a public release. there's a few things i'd like to polish up first though