Good quality plastics should be able to keep their natural colours as long as you don't leave it in the sun all day long which is the case. You should be more worried about accidently staining it instead when rubbed against a dirty surface.
I do agree white is a sexy and eye catching colour (just think of FW's XMM episode at macs ) and likely it will also win over some of the more fickle buyers with their uniqueness.
Hmm, what XMM episode? How come I didn't know?