We spend years in elementary school learning how to mix paints to create a desired color. Mixing all of the paints together made a dark color–black, dark brown, dark gray. Yet this doesn't happen with colors of light. A rainbow of colors of light makes white light. Proof? A beam of white sunlight passing through a prism creates a rainbow of color.
See example of a color space using red, green, and blue light.
Dueling Light Beams – Low cost way to mix beams of colored light—requires no software.
Make Colors — Prediction — This activity is also found under Challenges: Three Color Challenge.