Color Overview

Color Overview

Color is frequently used to symbolize information on maps. In recent years, cartographers have begun to employ color more frequently. in a study of map-color use in scientific journals, White et al., (2017) found that the use of color in published map figures increased from 18.4% in 2004 to 69.9% in 2013. This trend can primarily be attributed to the expansion of practical map production technologies. The cost of color printing, for example, is no longer prohibitory. Additionally, the increasing popularity of web-based dissemination of maps and other visual graphics makes such color production costs irrelevant. Tools such as ColorBrewer Colorbox, and Colorgorical have also made color selection easier; the first of these is now integrated into the color selection tools in ArcGIS Pro and a separate package in R (RColorBrewer).

Figure 5.1.1: ColorBrewer (left), and Color Schemes in ArcGIS Pro (right).

Credit: Cynthia Brewer, Mark Harrower and The Pennsylvania State University: ColorBrewer2.org(link is external); Screen capture from ArcGIS Pro.

In this lesson, we will explore the basics of specifying, mixing, and selecting colors for choropleth maps. You should aim to understand and properly apply the color schemes available in GIS software, and alter them as appropriate based on your maps’ audience, medium, and purpose. Eventually, you might even design your own color schemes from scratch.

Figure 5.1.2:: A choropleth thematic map from the Census.

Credit: United States Census Bureau(link is external)

You may remember the map in Figure 5.1.2 from Lesson 1. This map is a thematic map, and more specifically, a choropleth map. Discussions of color in mapping often focus on choropleth maps. This is for good reason—choropleth mapping is the most common thematic mapping technique, and its employment typically requires thoughtful analytical use of color. We will discuss the details of choropleth mapping later in this lesson. However,note that color is also frequently used on other types of maps. General purpose maps often employ color to delineate between different kinds of features, and maps that focus on other symbolization types (e.g., proportional symbol maps) often also use color to encode an additional variable, or to add visual interest.