Fading to blue screen

During working on the Power Mac G5, the screen fades to blue, then eventually back, and then fades again.. making work impossible. During the faded to blue part, the Mac is unresponsive, but queues the keystrokes in buffer, so raising the volume keystroke eventually gets processed, maybe a minute later... Also, when in faded to blue screen state, the fans rev up and down, in a repetitive cycle.. I lost my DVD with the apple hardware test.

Does anyone know what could be wrong?

Thanks,
RMSe17

The problem ended up being one of the monitor's lose connection. When I tightened the screws for the monitor plugs into video card, the problem went away.