Color theory begins with the two principal models that explain how color is created: additive and subtractive mixing. The additive model, known as RGB, is the basis for screens and digital displays, where red, green, and blue light combine to form all visible colors. Combining all three at full intensity produces white, which reflects how displays emit light directly to our eyes. The subtractive model, CMYK (cyan, magenta, yellow, and black), governs printing and painting. Here, pigments absorb (subtract) wavelengths from light; layering the three colors theoretically produces black, though printers add a true black ink for depth, richness, and detail. The choice between RGB and CMYK has real consequences for designers, since digital work shines in additive spaces while printed materials depend on subtractive reproduction.
Building on these models, the color wheel organizes colors by their chromatic relationships in a circle, typically displaying twelve positions: three primary colors, three secondary colors, and six tertiary colors. In the additive RGB model, the primary red, green, and blue combine to make the secondaries cyan, magenta, and yellow. In the traditional artist's RYB model used in painting, the primaries are red, yellow, and blue, and their combinations produce the secondaries orange, green, and purple. Tertiary colors fill in the gaps by mixing a primary with an adjacent secondary, producing nuanced hues like red-orange, yellow-green, and blue-violet. Sir Isaac Newton introduced this circular arrangement in 1666 after using prisms to split white light into a spectrum, and his wheel still underpins modern color theory.
Beyond the technical, the color wheel is also a tool for identifying warm and cool color families. Warm colors, including reds, oranges, and yellows, are linked to fire, sunlight, and energy, and they tend to advance visually toward the viewer. Cool colors, including blues, greens, and purples, evoke calm waters, sky, and nature, and they tend to recede. Understanding this warm-cool axis is essential for creating depth and mood, because painters and designers exploit it to suggest atmosphere, distance, and emotion even before considering specific color combinations.