I have a device with a blue LCD display where the backlight is blue and the letters are white. When I take photos of it with a cheap webcam, you cannot see any letter, because the blue light is too dominant. Does anybody have a cheap solution to this problem?
Mount a strong yellow filter, the display will image as black and the letters light yellow. If you can find some yellow cellophane X-mass wrapping ribbon or candy wrapping, you can experiment. If you like the effect, then buy a deep yellow photo grade filter. These were common in the black & white era. You can also buy a deep yellow gel filter. These are common in the theatrical stage lighting business. Likely if you look, you can find a piece of yellow flat glass or plastic to test this effect.