For 8 percent of men, color blindness is not just a fashion inconvenience, but an impairment that makes reading maps and other visual data difficult if not impossible. Now, a Penn State geographer has developed color schemes that allow most color-blind people to interpret the images.
"Rainbow schemes are very popular in maps designed to convey information," says Cynthia A. Brewer, associate professor of geography. "Unfortunately, rainbow schemes are not necessarily the best way to present information to most color-blind individuals."
Color blindness is not a single problem but a variety of problems that affect color vision. Only a very small portion of people do not see color at all, but view the world in shades of gray. The most common type of color blindness is red/green, which has two forms. Some people are missing red receptor cones and others are missing green receptor cones. People with different forms of red/green color blindness have slight differences in the way they perceive color. Another form of color blindness is blue/yellow, which is less common. While only 8 percent of men are color-blind, they make up 95 percent of the 9,000,000 people in the U.S. who suffer color-vision impairment.
"I am only attempting to accommodate those who are red/green color blind because combined they are the most common forms of color blindness," says Brewer. "It would be a different and more difficult task to accommodate everyone on the same map."
The reason one solution will not work for all types of color blindness is that color confusion occurs along lines through the full color space enclosed by the spectrum. Different sets of confusion lines are specific for the type of color blindness. Luckily, the confusion lines for both types of red/green color blindness, while different, are similar enough that colors can be chosen to serve both sets of individuals.