The different combinations of colors produced by red, green and blue are shown in the graphic below. The result of adding two primary colors of light is easily seen by viewing the overlap of the two or more circles of primary light. The lights are often the shape of circles. The light box illuminates a screen with the three primary colors - red (R), green (G) and blue (B).

The addition of the primary colors of light can be demonstrated using a light box. For this reason, many television sets and computer monitors produce the range of colors on the monitor by the use of red, green and blue light-emitting phosphors. In fact, the mixing together (or addition) of two or three of these three primary colors of light with varying degrees of intensity can produce a wide range of other colors. This is often represented by the equation below: R + G + B = W When red, green and blue light are mixed or added together with the proper intensity, white (W) light is obtained. The most common set of primary colors is red (R), green (G) and blue (B). There are a variety of sets of primary colors. Any three colors (or frequencies) of light that produce white light when combined with the correct intensity are called primary colors of light. White light can also be produced by combining only three distinct frequencies of light, provided that they are widely separated on the visible light spectrum.

But combining the range of frequencies in the visible light spectrum is not the only means of producing white light. When we speak of white light, we are referring to ROYGBIV - the presence of the entire spectrum of visible light. We have already learned that white is not a color at all, but rather the presence of all the frequencies of visible light. The subject of color perception can be simplified if we think in terms of primary colors of light. Yet your eye-brain system interprets the frequencies that strike your eye and the shirt is decoded by your brain as being purple. In such an instance, there may be several frequencies of light striking your eye with varying degrees of intensity. Consider for instance that you are looking at a shirt and it appears purple to your eye. When you look at an object and perceive a distinct color, you are not necessarily seeing a single frequency of light. Color perception, like sound perception, is a complex subject involving the disciplines of psychology, physiology, biology, chemistry and physics.

Complementary colors to blue