Delta-gun shadow mask operation. By User:Tirante (Own work) [CC BY-SA 3.0], via Wikimedia Commons A shadow mask colour CRT has three electron guns, one for red, one for green, and one for blue.

But cathode-ray-tube monitors function in a fundamentally different way from LCD screens, using an electron gun and ring of magnets to direct a beam across the screen. The inside of the screen is ...