well, let's try a few basic things...
1) have you tried restarting your computer?
2) how does everything else look? ie: windows desktop, web browser, etc... do THEY have the purple thing going?
3) have you updated your video drivers? (I usually don't have color problems, I just suddenly crash when zoning, that's when I know I need to check 'em LOL)
4) this is just reaching and I don't really think it'll help, but who knows... defrag?
short of that, I would suggest a remove/reinstall, but I'm not SOE support. LOL