rgbtest
rgbtest - LCD Dead Pixel Test
To get the last release version, please use the PPA:
https://launchpad.net/~chipmunk.sm/+archive/ubuntu/ppa
F1 - Help on/off
F2 – Switch color (white-red-green-blue-black)
F3 – Gradient ↔ Solid
F4 – Gradient direction
F5 – Fullscreen ↔ Normal