There are two techniques for producing color displays on CRT screens: the beam penetration method, which uses two phosphor layers to produce color depending on the electron beam's penetration depth, and the shadow mask method. The shadow mask method uses three color phosphor dots - red, green, and blue - at each screen point, along with three electron guns to control the display of each color separately, allowing for higher quality color pictures. Color variations are produced by varying the intensity of the three electron beams.