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Web Accessibility Basic Concepts - Wells Fargo
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Color Blindness

Color-blindness does not literally mean that a person can't see any color at all (except in very rare cases). Color-blindness refers to the inability to distinguish between certain kinds of colors, especially colors that are of equal brightness or luminosity, even if the colors themselves appear quite different to people without color-blindness.

Difficult Color Combinations for People Who Are Colorblind

There are several kinds of color-blindness, and varying degrees within those types, so it is difficult to provide a precise explanation of which color combinations are the worst for people who experience color-blindness, but here are a few of the more common types.

Red and Green

The most common form of color-blindness is red-green color-blindness, which makes it hard to distinguish between reds, oranges, and greens. Below are a few examples of the types of colors that can be easily confused. Can you see the numbers in each of the circles?

Red circle with a green number 6 inside orange circle with a green number 8 inside
green circle with an orange number 45 inside green circle with a red number 56 inside

The row of images below is adjusted to approximate how someone with red-green color-blindness might see the images. The numbers are very difficult to distinguish this way.

adjusted version of the first circle adjusted version of the second circle, which looks almost identical to the first
adjusted version of the third circle adjusted version of the fourth circle, which looks almost identical to the third circle

In case you have trouble seeing the numbers in any of these images, here is an explanation: The number six appears in the first circle (green numeral on a red background). The number eight appears in the second (green numeral on an orange background). The number forty-five appears in the third circle (orange text on a green background). The number fifty-six appears in the fourth image (red text on a green background).

Red and Black

Red and black can be difficult for some people to distinguish. Here is the unaltered version:

Red text saying 'Return of the Red Baron' in red text on a black background

And here is a version as it might appear to some people who cannot distinguish well between red and black:

same image as above, but desaturated

All colors

In very rare cases, a person's vision can be insensitive to all colors, rendering the world in a type of grayscale. Here are the same images from the examples above, modified to appear in grayscale:

grayscale version of first circle grayscale version of second circle
grayscale version of third circle grayscale version of fourth circle

Color-Blindness on the Web

Never use color as the only way to distinguish information

Bad Example

The table below uses color to convey the level of difficulty of the classes. Some people with red-green color-blindness may have difficulty distinguishing between the colors.

Original Table

JavaScript Courses
Course Title Level*
Angular.js  
Node.js  
JQuery  
Introduction to JavaScript  

*Red = advanced, Yellow = intermediate, Green = beginner

How the above table might look to someone with color-blindness:

JavaScript Courses
Course Title Level*
Angular.js  
Node.js  
JQuery  
Introduction to JavaScript  

*Red = advanced, Yellow = intermediate, Green = beginner

Assistive Technologies for People with Color-Blindness

There aren't many assistive technologies for people with color-blindness. For the most part, it is a condition that people just have to live with. A company called EnChroma claims to have developed glasses that can help compensate for some kinds of color-blindness. http://enchroma.com/ Their products may be worth checking out if you experience color-blindness.

 

Access a printable summary of considerations for all disability types.

Color-Blindness
Limitations

Color blindness, or color vision deficiency, is the inability or decreased ability to see color, or perceive color differences, under normal lighting conditions.

  • Partial color-blindness: Difficulty distinguishing between certain color combinations
    • Red/green color-blindness (For some people, this extends to red/green/orange/yellow)
    • Red/black color-blindness
    • Other color combinations (rare)
  • Total color-blindness ("monochromacy," very rare): The equivalent to seeing in shades of grey, black, and white
Assistive Technologies None, usually. Some people with monochromacy also experience low vision and may use a screen magnifier and/or a screen reader.
Input Methods No special input methods, usually, except for those who also have low vision (see the "Low Vision" table above)
Input Design Considerations No special considerations, usually, except for those who also have low vision (see the "Low Vision" table above)
Output Methods No special output methods, usually, except for those who also have low vision (see the "Low Vision" table above)
Output Design Considerations Avoid relying on color alone to convey information. Supplement color with other techniques such as text explanations, patterns, etc.

Related Links: Color Blindness

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