Why do paints often use primary colors?
Short answer
Paint uses a few basic colors as a starting point for mixing many other colors. Thinking in terms of primary colors makes the mixing system easier to organize.
How it works
Paint absorbs some wavelengths of light and reflects others. When different paints are mixed, they absorb more kinds of light, leaving less light to reflect. That is why mixtures often become darker.
Art lessons may describe red, blue, and yellow as basic colors, but real paints are not perfect primary colors. Printing commonly uses cyan, magenta, and yellow, while screens use red, green, and blue. The useful set depends on the purpose.
Key point
“Primary colors” is a model for organizing color mixing. It does not mean that every color can be made perfectly from exactly the same three paints.