Is this the white Ice book? G3? They do tend to turn. What I got was an iSkin (google it... I think the url is www.iskinz.com but I might be wrong) but one temporary way to get rid of the hand-oil coloration is to use isopropyl alcohol, 99% and rub well with a cotton ball.
I got mad at my icebook and just pulled the pyrex (pyrex?) clear top and bottom off, stripped the white paint off with alcohol and painted it stained-glass blue to hide the discoloration...