If it were black it would go grey and dull with time, so same problem
I used a light rubbing compound on my A500 and it worked great. Get one without silicone, though. Silicone goes yellow.
Auto Glym comes recommended for both cars and computers
-edit: Auto Glym paint renovator is the product. It leaves a wax in there as well, so if you spill anything on it, it's easier to clean.
