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California State University, Long Beach
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Color

What's the big deal about color?

Web designers need to make sure that the use color to display information is not the only method used to display information on the web site. Information displayed with just the use of color prohibits people with deuteranopia (red/green color deficit), or tritanopia (blue/yellow color deficit) from visually seeing the information that may not be in plain text elsewhere.

How do I fix this problem?

Just make sure that all of your images, graphs, or tables that display color also display the information in plain text format.

Below are examples of how end users who are color blind may view web sites that depend on color alone to transmit information:


This is the Earth

This is how the world looks
to a person with a red/green color deficit (deuteranopia).

This is how the world looks to a person with a blue/yellow color deficit (tritanopia).

The Earth
The Earth to  a person with deuteranopia
The Earth to a person with tritanopia

This is an Ishihara plate commonly used to check for red/green color blindness

This is what a red/green colorblind person might see. Note that the digit (3) is practically invisible.

An Ishihara plate with a green number 3 in the center of a red circle
An Ishihara plate where the green number 3 is practically invisable due to deuteranopia

More examples:

Protanopia hats,
unable to see red.

Deuteranopia hats,
unable to see green.

Normal hats.

Different colored hats.
How hats appear to someone with protanopia.
How hats appear to someone with deuteranopia.

Normal poppy flowers.

Protanopia poppy flowers, unable to see red.

Tritanopia poppy flowers, unable to see blue.
Normal poppie flowers.
How poppie flowers appear to someone with protanopia.
How poppie flowers appear to someone with tritanopia.

* For an expanded explanation on this procedure, view W3C Guideline 2: Don't rely on color alone.


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