It is probably the wires for the monitor. If the cable becomes twisted the wiring inside of the cable can break and short out the color. It may also be that when it was plugged in one of the prongs got bent! Unplug the cable from the computer and look at the prongs on the male side of the plug and see if any are not straight, this is the fast and easy, from the look for kinks in the cable. You can have a new cable installed or repaired in some instances.
It could be that you need to adjust your contrast, or it is getting ready to die on you. Sorry I can't be of more help, good luck.