A week or so ago Lissanna posted about a Blizz Twitter regarding potential graphical updates for moonkin & tree forms in Cataclysm, commenting that more than a redesign of the moonkin form itself, what would really be nice would be more color options for moonkin form, linked to caster form hair colors like the bear form and kitty form colors.
My druid, Kerisa, was happy with her kitty form color and, being a Boomkin, almost never uses her bear form, so she felt no need to rush out and change her fur color when the new feral forms debuted. If more color options for moonkin form (and/or tree form) were made available, though, she would definitely give serious consideration to changing her color.
Then I was out battling the rogue owlbeasts on Azuremyst Isle with Kamaliya, and seeing the two different colors of those owlbeasts there got me to thinking — could I find enough colors of wild owlbeasts out in the world to match them to the Tauren fur colors? After all, one can find wild cats and bears in colors which match the Tauren druid bear and kitty form colors reasonably well. So I went looking, and lo and behold, I did!
Red and red+spots and red with white belly (for males)
Tan and tan+spots and tan with white belly (for males)
This owlbeast is the same color scheme as the current Tauren Boomkin, albeit with antlers.
Blonde and blonde+spots and blonde with white belly (for males)
Gray and gray+spots and gray with white belly (for males)
Black and black+spots and black with white belly (for males)
This owlbeast is actually a Night Elf Boomkin, the darkest color of owlbeast currently in the game — there are no black wild owlbeasts.
For Night Elven druids, I imagine the moonkin form colors being purple (the current color), indigo/blue, red-violet, blue-black, and lilac-white, analogous to their bear and kitty colors.