Run the extended test on the LCD screen,if you recieve any errors or problems the screen will need to be replaced.

Or you could simply have some dead pixels in the screen if you do not want the dead pixels the screen will still need replacing. This is a first, i have never seen/heard of a user with dead pixels?...

Thanx for the assistance, dgkpcon.  Ran the tests, and nothing looked abnormal.  Did not get the purple pixels flickering during the test at all - the screens were undistorted.  But as soon as I booted into Vista, there they were.

My logic about this is during the tests you get isolated colors in stripes other colors which are a Red Green Blue Combo purple being a red blue missing the green on some pixels and they so tiny on the tests you probably wouldn notice because of what I call optical illusion of having so many stripes different solid colors on screen.

I recommend the same dgkpcon when normal test finish (the  dos mode blue backround white text test) it will ask you if you wish to continue with extended tests, say no!! And a true more powerfull diagnostics tool is loaded with a nice?! GUI run those tests and see however dead pixels or stuck pixel in your case are uncommon these days but can still happen run a tool like http://www.softpedia.com/get/System/Benchmarks/Dead-Pixel-Tester.shtml

and thats forces pixels to work hard and if you have stuck pixels another trick is trying to gently "massage" the area with a soft cloth Ive heard that b4 never had the chance to try it though...

http://www.albinoblacksheep.com/flash/rgb

you have some controls on that last one if you suffer from epilepsy dont run or click that last test I linked

its a live test running on the web.