Color theory is multifaceted, but can basically be reduced to three categories: color harmony, color wheels, and use of color. The human brain responds better to more harmonious visuals—things that are very bland, or overwhelmingly bright and busy, are harder to process. Color harmony describes formulaic sets of colors that are harmonious together. These schemes can each be represented by the placement of colors on the color wheel: analogous colors (colors next to each other), complimentary colors (colors that are directly opposite each other), triads (three colors that form an equilateral triangle), and split-complimentary colors (sets of complimentary colors with one color split into two analogous colors).
The modern color wheel contains the three primary colors (red, yellow, blue), three secondary colors (orange, green, violet) and six tertiary colors (red-orange, red-violet, yellow-orange, yellow-green, green-blue, blue-violet). It is said that Isaac Newton created the first color wheel in the 1660s after discovering that by passing light through a prism, he could create a rainbow. His wheel, therefore, was his arrangement of the EM spectrum broken into discrete packets of light. Note that if you spin the wheel fast enough, the colors blend together such that your eye will see white. Newton’s original wheel contained seven colors (our ROYGBIV). In addition, he likened the colors to musical notes and made each spoke of the wheel a note from the Dorian mode C-major scale.The presence of colors, and their interactions with one another, influences our perception of an environment or object. This is known as “color psychology,” and has been the subject of many recent studies. For example, research has looked at how consumers perceive the “personality” of a brand based on its marketing colors. To get an idea of how color can change perception, take a look at the same printed image in front of three very different backgrounds. The white background has the least influence on the image—one reason why most art museums have white or off-white walls. In my eyes, the striped green and blue background brings out the contrasting warmer colors (pink and yellow), while the yellow background seems to accentuate the cooler colors. Even if colors do not change the functionality or utility of your design, they can have a big impact on how well it is received by your audience.
For more on color, see my previous blogs In living color and If trees taught coloring.