Together the lights form white light on the screen. This exhibit illustrates properties of light and color.
White light is made up of red, blue and green light waves.
When a person stands in front of the screen, each light casts a separate shadow. In the region where the green light is blocked, the red and blue lights combine to form magenta. In the region where the blue light is blocked, the red and green lights combine to form yellow. By adding various amounts of red , green, and blue light we can produce any color in the spectrum. For this reason, red, green, and blue are called additive primary colors .