If that doesn't help, look online for a color map, preferably with lables (like this one maybe) and look at it on a known good monitor and go to ctrl panel > display >Settings >advanced and look for a tab that says color adjustment (or just look through them until you find one) and move stuff around untill the colors are as they should be.
Its probably the drivers. If you built a new computer, then you need to install the drivers for the video card. I'm assuming you have a nVidia video card, if you do, and you have Win2K or WinXP, then this is the link to download the drivers.
did you buy that card without realizing it was the absolute best card you could possiby get? at the mo, the only thing better than a 7800GTX is two of them! lol