Color
Simple palette
Many different hues on a map can complicate reading. Most people can only hold seven or so “things” in working memory. People may see hues as different “things,” making a map with many different hues appear busy.
Consider developing a simple palette, using only a few hues and use figure-ground reversals along with size, shape, value, and texture to increase the map’s vocabulary. Many old highway maps used only red and blue (with or without black) to create a minimalist aesthetic.
Saturation pops
Highly saturated colors will pop, draw the eye, and rise to the top of your visual hierarchy. Too much saturation may overwhelm a reader’s senses or just tire them out.
Unsaturate color for elements that you want to put in the ground. Increase saturation for elements that you want to emphasize and elevate towards the top of your visual hierarchy.
Consider the Pepsi Challenge ad campaign (blind taste test between Pepsi and Coke): When given one sip, most people chose Pepsi, because Pepsi had more sugar. But if people were asked to drink the whole can and then asked choose, they would pick Coke. Saturation is like sugar. Most people do not want to drink it all day long.
Candle-lit canvas
A pure white background to a map reflects much light, calling attention to it.
Approach a printed map as a draftsman would centuries ago – put your marks on a light-colored canvass, building your map’s depth upwards. Don’t fill the whole background with a dark hue. Mimic the look of candlelight on the paper or the age of paper by adding warm subtle tone to the background, so that it does not appear pure white, but take care not to reduce too much of your contrast range.
Light through the keyhole
When color fills a very small area, hue becomes difficult to distinguish and value becomes the most salient color variable.
Hues that appear near each other on the color wheel will be particularly difficult to distinguish in small fills. Similarly, hues that are similarly dark in value (like blue and green) are difficult to distinguish when printed as tiny dots; the two hues will appear similarly as “some dark color”. When making dotted lines or very small point symbols, avoid using hue as a visual variable to distinguish different kinds of point or line features. Consider using texture, value, or size instead.
Stop with the stoplight
About six percent of men have impaired color vision and will have difficulties distinguishing between colors. Search tasks will be difficult for them when hue is used as the primary distinguishing variable, or when hue is used as a variable for organizing information.
When designing maps that are “universally” accessible, choose unambiguous color combinations, use alternative visual variables (e.g. shape to distinguish kinds of things, size to distinguish quantities of things), and/or directly annotate features.
Get over the rainbow
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