In color theory, color harmony refers to the property that certain aesthetically pleasing color combinations have. These combinations create pleasing contrasts and consonances that are said to be harmonious. These combinations can be of complementary colors, split-complementary colors, color triads, or analogous colors. Color harmony has been a topic of extensive study throughout history, but only since the Renaissance and the Scientific Revolution has it seen extensive codification. Artists and designers make use of these harmonies in order to achieve certain moods or aesthetics.

Several patterns have been suggested for predicting which sets of colors will be perceived as harmonious. One difficulty with codifying such patterns is the variety of color spaces and color models that have been developed. Different models yield different pairs of complementary colors and so forth, and the degree of harmony of sets derived from each color space is largely subjective. Despite the development of color models based on the physics of color production, such as RGB and CMY, and those based on human perception, such as Munsell and CIE L*a*b*, the traditional RYB color model (common to most early attempts at codifying color) has persisted among many artists and designers for selecting harmonious colors.

Complementary colors exist opposite each other on the color wheel. They create the most contrast and therefore greatest visual tension by virtue of how dissimilar they are.

Split-complementary colors are like complementary colors, except one of the complements is split into two nearby analogous colors. This maintains the tension of complementary colors while simultaneously introducing more visual interest with more variety.

Similarly to split-complementary colors mentioned above, color triads involve three colors in a geometric relationship. Unlike split-complementary colors, however, all three colors are equidistant to one another on the color wheel in an equilateral triangle. The most common triads are the primary colors. From these primary colors are obtained the secondary colors.

Similarly to color triads, color tetrads involve four colors in a geometric relationship. Color tetrads form a rectangle on the color wheel.

The simplest and most stable harmony is that of analogous colors. It is composed of a root color and two or more nearby colors. It forms the basis for a color scheme, and in practice many color schemes are a combination of analogous and complementary harmonies in order to achieve both visual interest through variety, chromatic stability, and tension through contrast.

It has been suggested that "Colors seen together to produce a pleasing affective response are said to be in harmony". However, color harmony is a complex notion because human responses to color are both affective and cognitive, involving emotional response and judgement. Hence, our responses to color and the notion of color harmony is open to the influence of a range of different factors. These factors include individual differences (such as age, gender, personal preference, affective state, etc.) as well as cultural, sub-cultural and socially-based differences which gives rise to conditioning and learned responses about color. In addition, context always has an influence on responses about color and the notion of color harmony, and this concept is also influenced by temporal factors (such as changing trends) and perceptual factors (such as simultaneous contrast) which may impinge on human response to color. The following conceptual model illustrates this 21st century approach to color harmony: