The Muser
Physics & Physiology of Color

Return to
The Muser

The Color Musings
Additive Mixture
Subtractive Mixture
Complementary Colors
Primary Colors
Hue, Value, Chroma
Predicting Color Mixtures
Young's 3-color Theory
A 3-color System
Land's 2-color System
James Clerk Maxwell
Thomas Young
Hermann von Helmholtz
Edwin H. Land

Return to

Additive color mixture
Additive Color Mixture

This illustration simulates an experiment you can do with three slide projectors. Filter the light from the three projectors, so that one of them projects a circle of red light, one of green light, and one of blue. Align the projectors so the three circles overlap in the middle of the pattern.  For more detailed information on the demonstration, send e-mail to The Muser.)


There are two ways to mix colors. If we mix light, we call it additive mixture.  When we mix inks, dyes or pigments, that is subtractive mixture. There is really no difference in the way the colors behave in the two circumstances. Only the mechanics of the processes are different.

Additive color mixture begins with the absence of light (black), and adds colors of light together to form new colors.  The illustration shows how this kind of mixture might be done with three slide projectors.

Red, green and blue are typically used as the additive primary colors. In pairs, they combine to create cyan, magenta and yellow. When all three of the additive primary colors are added together, in approximately equal intensities, they produce white light.

Additive mixture is used in theatrical lighting, and in computer monitors and TV screens. (Examine your computer screen or TV with a very strong magnifying lens, and you'll see that the image consists of a matrix of red, green, and blue dots, or pixels.)

How does this additive mixture work? It's no mystery really, and it has little or nothing to do with the physiology of our eyes or brain. This is simple math.

Spectrum The red color we use for additive color mixture is composed of the light from one-third of the spectrum. The green color is another third of the spectrum. And the blue color is the remaining third.

Where two colors overlap, or are added together, their combined light accounts for two-thirds of the spectrum. (1/3 + 1/3 = 2/3) Those combinations always produce the colors cyan, magenta, and yellow. Where all three colors overlap, the entire spectrum is present, so we see white light. It's that simple.

This demonstration of additive color mixture lays the foundation to the understanding complementary colors, subtractive color mixture, and primary colors.

What are complementary colors?
They aren't colors that talk nice to each other. But they can blow your mind!

What are primary colors?
They may not be exactly what your first-grade teacher said they are.

Can color mixtures be predicted?
You bet.

© J. C. Adamson, 2001