Q:
A: If it's the whole monitor that's purple than it's probably a bad cable. Wiggle the cable at either end and see if it goes away/changes colors. A VGA cable carries red, green and blue information to the monitor so it's probably a couple pins or wires that are wearing out. Magnets are only a problem if using a CRT monitor. If that's the case, look for a de-Guass setting to demagnetize the screen. It might take a few tries but overtime its fixable.