Color scheme



A Color scheme is a collection of multiple colors chosen to be used together on a graphical work, such as a map. In Cartographic design, strategically chosen color schemes can achieve a number of goals, including harmony, contrast, conveying information, and showing the relationships between features on the map. The term is most commonly used for statistical thematic maps, in which color is used to represent quantitative and qualitative attribute values.

Diverging Schemes
Diverging color schemes are best used to highlight both high and low extreme values, or values that differ significantly from the norm. Also, this color scheme is usually for used for data that include a critical midpoint value (mean, median, or zero value) and a data distribution that includes two ends of importance. This is done using "two complementary color schemes that diverge from a common hue."

Sequential Schemes
Sequential color schemes are logically arranged from high to low and is often used in creating a map with sequential lightness steps. These data do not usually contain a critical midpoint value, but contain a range of values. For example, lower data polygons can be represented by lighter colors while the higher value polygons are represented by dark colors.

Qualitative Schemes
Qualitative schemes show differences between categories with different hues; lightness should be similar, although small lightness differences are necessary for the colors to be distinguished from one another and allow areas to be identified more easily. There should be no large differences in lightness or saturation because these imply differences in importance. A sub-category of Qualitative Schemes is a Binary Scheme, where nominal data are divided into only two categories (yes/no, pass/fail, public/private, etc). Binary Schemes usually use a lightness step to display the two category data, such as grey-white, light blue-dark blue, etc.