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Before getting into the details of the types of color-blindness, you should know that the following explanations are simplified versions of the complete picture. Color-blindness is a fascinating topic precisely because of its complexity. You do not need to understand all of the details of color-blindness to know how to create web content that is accessible to those who are color-blind. Here is an important fact to understand right off the bat:

Important

The key principle of web accessibility for users with color-blindness is:

The colors with which they have difficulty distinguishing depend upon their type of color-blindness, but red-green deficiencies are the most common.

The most common broad category of color-blindness is often called red-green color-blindness, but this does not mean that these people cannot see reds or greens. They simply have a harder time differentiating between them. Not all reds and greens are indistinguishable. It would be easy for someone with a red-green deficiency to tell the difference between a light green and a dark red, for example. A lot dependsat least in parton how dark the colors are. If the red is approximately as dark as the green, there is a greater likelihood that the colors will be confused.

Also, there is some evidence that people with red-green color-blindness see reds and greens as yellows, oranges and beiges. This means that yellows, oranges, and beiges can be confused with greens and reds. The colors least affected are the blues.

When designing web content for people who are color-blind you do NOT have to convert all of your images to black and white or get rid of your images entirely. In fact, you may not have to change any of your images at all. Here is the key:

Important

Make sure that colors are not your only method of conveying important information.

Most of the time when people put images on the web, the fact that they are in color at all is irrelevant. It may be nicer to see the colors, but the viewer can understand the image just fine even with all of the colors removed. If, however, the purpose of posting the image is to communicate something about the colors in that image, then it is important to provide some other way of understanding the information. For example, if the image shows the routes of the London Underground, where the routes are distinguished only by the color of the lines, as in the graphic below, you would want to somehow annotate either the graphic itself (and supply the appropriate alt text) or the text in the web page to supplement the color-dependent method of distinguishing between routes.

Incidentally, people with color-blindness are not the only ones who will benefit from this technique. Those who are blind are also unable to distinguish between colors, and so are in need of the extra cues given through other methods.

Read this article:
WebAIM: Visual Disabilities - Color-blindness

This entry was posted on March 27, 2019 at 8:44 am and is filed under Blindness. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |