While I'd love colored MacBooks, I don't see it happening anymore. Apple learned that releasing multiple colors of higher end devices like computers resulted in many many unsold disliked colors. iPods are different since they're cheaper and easier to discard if unsold. Lower margins and such.
Now, if they DID release colors again, especially in the iPod colors, I would totally choose either a yellow or orange one. Or the red. Mmm... I'd probably look at them all and decide then. But it'd be between those three.