My monitor seems to be displaying a teal overlay on things. It seems to effect somethings more than others, so, for instance, blues look really bad, as do photographs. But you can't really notice it on my FOFC skin, MacOSX, which is mostly white. Is this a graphics card thing (which I don't think is as likely because when I activate my second monitor it displays colors correctly) or does it mean my 6 month old monitor is messed up?

Often this is a sign that a pin in your monitor cable is bent.. have you plugged/unplugged the monitor recently?