I am running Ubuntu 12.04 on an HP laptop with a broken screen. I have it hooked up to an external monitor. It's been running fine this way for close to a year, but now the screen is tinted blue. I've checked monitors, cables, even borrowed an expansion base and used those outputs and it still does it.
Normally this would be caused by a hardware failure. If you have replaced the cables try a different monitor. If the different monitor works, then the problem is the monitor. If a different monitor is still blue, then it's likely the mother board.
A fast way to tell, is the color blue during boot? If so, it's hardware (specially if it's during BIOS POST).