Suspect dead pixels in your display? If so, then you can quickly catch with this little app. This app starts in full screen mode and show you first a blank white screen. Here you can identify any defective pixels already on the display at the same time, since these are mostly black.
With every touch of the screen, the background color changes to be able to recognize how strongly the possibly existing pixel error shows in the different representation. After 6 color sweeps you start again with the white screen.
MORE THIS APP CAN NOT! This is done by design!