If you see the color change, or the color returns to normal, your electron gun is out of alignment and will get worse over time.
To see if your electron gun is out of alignment, lightly tap the side of the monitor. If your's doesn't have a degaus button, try searching through your menu for the degaus option by hitting the monitors menu button. Most CRT Monitor's have degaus button (usually marked by a symbol of what kind of resembles a horseshoe) which if pressed will degaus the monitor. Lastly, as this is a CRT monitor, you might need to Degaus the monitor or the electron gun could be coming out of alignment. If your monitor has the ability to removed the VGA cable from the monitor, you might try replacing the cable (most CRT monitors do not support removing the VGA cable though). IF they have become bent, you can usually carefully use a pair of tweezers to slowly bend them straight again (be careful because if you aren't you could break the pin off).
If it isn't loose, unplug the cable and see if any of the pins have become bent on the inside. First I would check the end of the cable that plugs into the computer, if this has become loose, it can cause discoloration.
