I made a thread a little while ago about what could be a similar problem.
If you find it blinking and making weird colors, try wiggling the screen itself to see if anything changes.
If it changes or makes the issue go away by wiggling the screen, then you might need to get a new set of wires for the screen. For me, I found that a plug just wasn't seated correctly or something. I took mine apart, unplugged all the wires and put them back in. No problems so far.
If it turns out to not be that, it could be a video driver issue. Try updating the drivers for your video card or, if you've done this recently, roll them back to an earlier version.
Hopefully it's nothing major.
Could you post what make and model it is?