Can someone explain basic color theory to me like I'm five?

Basic Color Theory. Color theory encompasses a multitude of definitions, concepts and design applications - enough to fill several encyclopedias. However, there are three basic categories of color theory that are logical and useful : The color wheel, color harmony, and the context of how colors are used.

3 categories: primary colors, secondary colors and tertiary colors

Explanation:

Color theory is both the science and art of using color. It explains how humans perceive color; and the visual effects of how colors mix, match or contrast with each other ... In color theory, colors are organized on a color wheel and grouped into 3 categories: primary colors, secondary colors and tertiary colors.