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. Color theory also involves the messages colors communicate; and the methods used to replicate color.
In color theory, colors are organized on a color wheel and grouped into 3 categories: primary colors, secondary colors and tertiary colors.
Color is perception. Our eyes see something, and data sent from our eyes to our brains tells us it’s a certain color. Objects reflect light in different combinations of wavelengths. Our brains pick up on those wavelength combinations and translate them into the phenomenon we call color.
Humans see colors in light waves. Mixing light — or the additive color mixing model — allows you to create colors by mixing red, green and blue light sources of various intensities. The more light you add, the brighter the color mix becomes. If you mix all three colors of light, you get pure, white light.
Any color you see on a physical surface uses the subtractive color mixing model. Most people are more familiar with this color model because it’s what we learned in school when mixing finger paints. In this case, “subtractive” simply refers to the fact that you subtract the light from the paper by adding more color.
Traditionally, the primary colors used in the subtractive process were red, yellow and blue, as these were the colors painters mixed to get all other hues. As color printing emerged, they were subsequently replaced with cyan, magenta, yellow and key/black (CMYK), as this color combo enables printers to produce a wider variety of colors on paper.
The first color wheel was designed by Sir Isaac Newton in 1666 so it absolutely predates your introduction to it in kindergarten. Artists and designers still use it to develop color harmonies, mixing and palettes.
The color wheel consists of three primary colors (red, yellow, blue), three secondary colors (colors created when primary colors are mixed: green, orange, purple) and six tertiary colors (colors made from primary and secondary colors, such as blue-green or red-violet).
Draw a line through the center of the wheel, and you’ll separate the warm colors (reds, oranges, yellows) from cool colors (blues, greens, purples).