I heard that this can solve artifacts, or in your case, strange colours :P .
Start >> Control Panel >> Display >> Settings (tab) >> Advanced >> Troubleshoot (tab) >> ENABLE WRITE COMBINING
If Write combining is unticked, tick it.
If it is already ticked, untick it
Sorry i can't remember which way it works. All i remember is that the option changes artifacts and strange colouring on alot of games. If it doesn't work Simply tick it on/off to it's default settings