LCD Monitor Problem and how to fix it

1. Bad connections inside the monitor, including electronic parts like capacitors, that might be defective
2. Faulty or loose cable connections at the PC or video end (check the connector pins)
3. Bad video card or display driver (this will require you to reinstall the graphic drivers)

All of these can cause monitor color problems - be it intermittent changes in color, or issues with brightness, size & screen position.
Try degaussing the screen if you're using a CRT monitor & keep any sources of magnetic interference away from the monitor. On an LCD monitor, try running it at the native resolution.