Magenta is a diagnostic, not just a colour
Pure magenta is red and blue at full power with green switched off entirely. That makes it a direct test of one specific fault: a pixel whose green subpixel is stuck on will show as a pale, washed out or white dot against the magenta field, because it is the only pixel in the frame emitting green at all. On a white screen that same pixel is invisible.
It works the other way too. If the whole screen looks pink when it should look white, on a monitor, a phone camera preview or a television, you are almost certainly looking at a green channel that has failed or a cable with a damaged pin. Open the green screen next: if it comes up black or patchy, the fault is confirmed and it is hardware.
The pink screen on a phone camera
A pink or magenta cast that appears only in the camera app, and only sometimes, is usually a software fault rather than a broken sensor. It is common enough on several phone models to have its own support articles. Restart the phone, clear the camera app cache, and check whether it also happens in a different camera app before assuming the hardware is gone.
Practical uses beyond testing
- A bright, flattering bounce light for close up video, warmer than white and less clinical.
- A high contrast backdrop for photographing pale or metallic objects that disappear against white.
- A quick visual check that a projector or television is not clipping saturated magentas, which show as flat blocks with no detail when it is.