Have you checked and made sure the RGB cable was connected on both sides? This can cause distortion in color and picture.
It might also be possible that it is a power issue. Perhaps you should plug it into a different outlet if that one is overloaded or faulty.
You might also try plugging in the computer into another monitor to check if it is the computer or the monitor that is the issue. If it is the computer then you might check the unit and clear out dust and make sure the fans are working.
Those are just some quick checks to see if it is a simple fix or a more serious issue.