With a computer on nearly every desk, mapping software is now available to just about everyone, but choosing colors for maps is a job often fraught with complexity and failure. Now ColorBrewer, a web-based tool created by Penn State geographers, can make choosing map colors fast and easy. "Lots of people have these new tools on their desk to allow mapping and data representation, but they do not have expertise in designing maps," says Cynthia Brewer, associate professor of geography. "In using these tools, people generally choose the default color schemes which may be inappropriate for the data or for the final format of the map."
ColorBrewer is intended to for people who do not want to spend too much time selecting a color scheme or fine-tuning one they have created. Mark Harrower, graduate student in geography, told attendees at the 98th Annual Meeting of the Association of American Geographers in Los Angeles today (March 23): "It is a free 24-hour on-demand color consultant."
The web tool is free, requires no registration and triggers no pop-up advertising. It is available at ColorBrewer.org and will run on Netscape or Internet Explorer. Users do need to have a free Flash 5 plug-in for their browsers, but they can download it from the site. While a full page of instructions is readily available, ColorBrewer can be used simply by opening the page and following the three steps indicated in the boxes. If at any time a user wishes to know more, a "learn more" button produces an explanatory pop-up box.
Step one in choosing colors is to choose the number of classes in the map. ColorBrewer allows from 3 to 12 classes, but the geographers warn that while larger number of classes makes the map more information rich, the map becomes busier and more difficult to interpret, the more classes it includes.
"One of the hardest things for a novice map maker to do is match the data set with the proper set of colors," says Harrower.
Step two therefore asks the user to chose the type of data -- sequential, diverging or qualitative. The sequential scheme is used for data that falls in ordered ranges, while the diverging scheme applies to data with a central point, for example a national average. Qualitative schemes are used for data that falls in categories.
Once a legend type is chosen in step two, the step three box shows a variety of color schemes that can be tested on a large map that appears to the right. The map shows not only blocks of color, but also has areas where small amounts of the various colors appear next to each other. While the sample map does not depict real data, but rather shows a carefully chosen pattern of color to help the user determine if a specific color scheme will work for them, it provides the necessary variety to test the color schemes for clarity and viewability. The web-tool also allows users to test color choices for type overlays, city symbols and road-like features. Borders can also be turned on and off.
ColorBrewer is not intended to allow viewers to upload their maps to the program, but rather to test color schemes. At any time while using the web tool, the user can change the number of classes, type of data and the color scheme. "The intention was to design a platform where someone can play with the color schemes and develop one that works, rather than spending the time and effort of designing on their map only to find that the colors chosen do not convey the information intended, or cannot be printed or projected," says Harrower.
As an added benefit, once the user chooses a color scheme, the program will print out the color specifications in a choice of designations including commercial printing, computer screen, web page, ArcView 3 color or CIE Lab specifications. In this way, whether the final product is to be projected, a published book, displayed on a CRT or LCD screen or placed on the web, the appropriate color code numbers appear. A key at the bottom left of the single screen display supplies further information about the chosen color scheme. A list of icons indicates if the color scheme will work for most color-blind people, will project well on a screen, will look right on a CRT or LCD, is printable using commercial processes or would be photocopyable. In some cases the indication is definitely yes or no, but in other cases a question mark appears, indicating that the scheme may or may not work in that media. The map maker will want to check these colors more carefully to be sure they work on their final map.
This project was funded by the National Science Foundation. Brewer produced the concept and the time-consuming color specifications and translations. Harrower created the Flash program and the Web interface design. Harrower will be joining the University of Wisconsin -- Madison in the fall as an assistant professor of geography.
You can find the tool online at colorbrewer2.org