A large percentage of the visible spectrum can be represented by mixing red, green, and blue (RGB) light in various proportions and intensities. These three colors are called the additive primaries . Added together, red, green, and blue light make white light. Where two colors overlap, they create cyan, magenta, or yellow.
The additive primary colors are used for lighting, video, and monitors. Your monitor, for example, creates color by emitting light through red, green, and blue phosphors.