The monitor screen has a bluish, greenish or purplish tint
Cause: This is usually caused by a break in one of the three colour signals between the video card and the monitor. The problem is especially common in older monitors, and is caused by heat stresses that break the connections between the cable and the circuit board inside the monitor.
Solution: Check the signal cable for kinks, frays and other signs of wear and tear. If the cable is not integrated, have it replaced, else take the monitor to the repair shop and they should replace it for you at very little cost.