Color scheme is a working model, set of algorithms and rules to build color combinations of given properties and purpose. Selected colors have to work together in an expected way, express a desired emotion or effect. There is an unlimited count of various color schemes, yet there are several basic scheme model designers can start with.
The major part of a color scheme is the count of main colors (hues) used within the scheme, and their ratio – how similar or unlike they are, what's the contrast and a tension among them. Usually one up to four main colors are used in color schemes. Five and more colors start to be too much to be tamed and to maintain the desired effect of the palette, only experienced artists and designers should use such a rich palettes. But usually, the most common 1–4 color models are good starting point to create a great color palette for any project.
Basic color scheme models
Another importnant parameter of a color scheme is the base color. This means, a base hue the model uses to specify all other related colors in the palette. Color schemes built on the very same model, based on deep red, bright orange, or steel blue color will look very different and express different emotions. Besides the base color hue and the choice whether the base is a warm color or a cold color, also its saturation and brightness are important, influencing the final look of the created color scheme.
The model and base color define only the main colors of the scheme, or in fact their hues. Anyway, this is typically too less colors for a practical use of a color scheme/palette. We need to pick various shades of each color – some lighter, some darker variants of each color, some paler and some more saturated. We can use many of various shades of each color within the scheme, while keeping it's look and feel. The number of shades for each color should be proprtional to the color importance: we should use most shades of the base color, less shades for secondary colors and only couple of them for accent colors.