eMac screen sometimes goes rainbow coloured?

This problem is caused by some magnets located near the screen, check to see if you have any speakers that are near and try moving them away, if not there may be a fault with the 'de-gausing' which should correct problems like this every time you switch the monitor on, this option should be on the monitors settings, try a search on google for the manual or have a look at the monitors settings

Simon
September 2006