I suspect there are few of hot pixels on my panel. As it is still under warranty and by the rules of my vendor I can replace a machine if panel has a 3 dead pixels on it, I'd like to check how many dead pixels there actually are. In Windows, there are plenty of simple applications that just fill the whole screen with different colors so hot/dead pixels are easily visible. Does something like this exists for Ubuntu?
This page just provides the white / black / red / green / blue screens to test your monitor: http://lcdtech.info/en/tests/dead.pixel.htm
You could use
GIMP Image Editor to make 4 images that are the same size as your desktop and color them red / green / blue / white.
Then open them in
Image Viewer ( default picture viewer ).
Then dual click on the picture to get it full screen.
GIMP Image Editor is available from the
Ubuntu Software Center
Following is a How-To for the visual learners.