FANTASTIC seems to work pretty good..use a rag, not paper.
Now I found something out by accident.......if you remove the entire plastic casing and dip it into a bucket of alcohol for a few hours........it removes the yellow and make it Whiter! but it removes the shiny enamel on the plastic and makes it very dry..but I guess one can put Armor-All right after that! :-)
I would experiment first by the way, with some plastic piece you dont need, such as the CDROM plate that is there before one adds a CDROM drive. Or take an A600, A1200 or A500 powersupply apart and test it with the plastic casing of that! :-) just fill a little bucket with the green alcohol (not sure about the clear one but it might work) and leave the plastic PSU case in there..make sure you leave the bottom half of the PSU outside the bucket and dont put it in yet...just to compre the difference in color to see if it worked.
See the way this happened was I had a real Yellow 1084s Monitor in which I left a bottle of Green alcohol ontop which apparently had dripped some........when I picked up the bottle the next morning, the spot was white..or at least the original color that the 1084 monitor was! :-) I want to try this with the Yellow A1200 I have here.especially with the keys..