Harmony and variety are vital compositional concepts. Harmony is when the elements work together. Harmony and discord can exist within various elements, such as color, shape, and tone. Within a single image, there can be harmony in one element and discord in another. For example, you may have color harmony, but a discord in the contrast of shapes.
Colors that lie close to each other harmonize. Harmonious images are more relaxing. They are calming
and easier on the eye. Bold colors can excite. Contrasting colors stand out and can create discord when used in roughly equal amounts. Shapes that are well placed also can achieve harmony.
Lines of force and points of interest can help achieve harmony in a composition. Shapes that complement each other help to create harmony. For example, interlocking shapes or shapes of varying sizes that echo each other appear harmonious.