PiXel Check is an application that assists you in visually inspecting your LCD flat-panel display for bad or "dead" piXels.

"Red" activates all red piXels, "Blue" activates all blue piXels, and "Green" activates all of the green piXels. The "Black" and "White" tests activate or deactivate all red, green, and blue piXels respectively.

The reason that red, green, and blue are the colors that are checked for is because each piXel on an LCD flat-panel display is actually made up of 3 separate transistors - red, green, and blue. When all of the transistors are turned on, you see black, and when all of them are turned off, you see white - the reason why there are also black and white check modes.