Although a high-quality map is composed of many different elements, color is one
Although a high-quality map is composed of many different elements, color is one of the first components noticed by end-users. This is because we each have an intuitive understanding of how colors are, and should be, used to create a compelling and pleasing visual experience. Nevertheless, it is not always clear to the mapmaker which colors should be used to convey the purpose of the product best. This intuition is much like listening to our favorite music. We know when a note is in tune or out of tune, but we would not necessarily have any idea of how to fix a bad note. Color is indeed a tricky piece of the cartographic puzzle and is not surprisingly the most frequently criticized variable on computer-generated maps. This section attempts to outline the essential components of color and the guidelines to most effectively employ this vital map attribute.
Color Basics
As electromagnetic radiation (ER) travels via waves from the sun (or a lightbulb) to objects on the earth, portions of the ER spectrum are absorbed, scattered, or reflected by various objects. The resulting property of the absorbed, scattered, and reflected ER is termed “color.” White is the color resulting from the full range of the visual spectrum and is therefore considered the benchmark color by which all others are measured. Black is the absence of ER. All other colors result from a partial interaction with the ER spectrum.
The three primary aspects of color that must be addressed in map making are hue, value, and saturation. Hue is the dominant wavelength or color associated with a reflecting object. Hue is the most fundamental component of color and includes red, blue, yellow, purple, and so forth. Value is the amount of white or black and is often synonymous with contrast. Variations in the amount of value for a given hue result in varying degrees of lightness or darkness for that color. Lighter colors are said to possess high value, while dark colors possess low value. Monochrome colors are groups of colors with the same hue but with incremental variations in value. Variations in value will typically lead the viewer’s eye from dark areas to light areas.
Saturation describes the intensity of color. Full saturation results in pure colors, while low saturation colors approach gray — variations in saturation yield different shades and tints. Shades are produced by blocking light, such as by an umbrella, tree, curtain, and so forth. Increasing the amount of shading results in grays and blacks. A tint is the opposite of shade and is produced by adding white to a color. Tints and shades are particularly germane when using additive color models. To maximize the interpretability of a map, use saturated colors to represent hierarchically prominent features and washed-out colors to represent background features.
If used properly, color can greatly enhance and support map design. Likewise, color can detract from a mapping product if abused. To use color properly, one must first consider