Color Vision Knowledge Base
Our color blindness knowledge base is designed to answer your questions and help you learn more about color blindness.




  Color blindness background

  Causes of color blindness

  Types of color blindness

  Clinical forms of color blindness

  Treatment for color deficiencies

  Questions and answers


Color Blindness Questions and Answers

What bothers color blind people most?
(1) A colorblind person is generally unable to interpret the chemical testing kits for swimming pool water, test strips for hard water, soil or water pH tests because they rely on subtle color differences.


(2) Many colorblind people cannot tell whether a woman is wearing lipstick or not. More difficult to handle for some is the inability to make the difference between a blue-eyed blonde and a green-eyed redhead.

(3) Color vision deficiencies bother affected children from the earliest years. At school, coloring can become a difficulty when one has to take the blue crayon - and not the pink one - to color the ocean.

(4) Bi-color and tri-color LEDs (Light Emitting Diodes): is that glowing indicator light red, yellow, or green? Same problem with the traffic lights...

(5) When grilling a piece of meat, a red deficient individual cannot tell whether it is raw or well done. Many cannot tell the difference between green and ripe tomatoes or between ketchup and chocolate syrup!

(6) Some food may look definitely disgusting to color vision deficient individuals: a plate full of spinach, for instance, just appears to them like cow pat. They can however distinguish some citrus fruits. Oranges seem to be of a brighter yellow than that of lemons.

How can color blind people compensate for their deficient color vision?
While there are no cures for color blindness, there are many possibilities to help control the annoyance of this disease. A possible treatment for color vision deficiency is to use special glasses with red-orange filters to make it easier to interpret colors or actually to better see contrasts. Another way to control symptoms is to use what is called the X-Chrom lens. The X-Chrom lens is a red contact lens worn on the non-dominant eye of color deficient people and which helps some to better interpret colors or contrasts. The X-Chrom lens does not restore normal color vision, it just allows some colorblind individuals to distinguish colors better.

How can teachers help if a student has a color vision deficiency?
Always use white chalk, not colored chalk, on the board to maximize contrast. Avoid yellow, orange, or light tan chalk on green chalkboards. Xerox parts of textbooks or any instructional materials printed with colored ink. Black print on red or green paper is not safe. It may appear as black on black to some color vision deficient students.

How do color vision deficient persons perceive a colorwheel?

Mouse over this standard colorwheel to see it as a colorblind person might see it.


color wheel

Are there 'false' color blind persons?
There is a type of color vision deficiency that is caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina. This kind of color vision deficiency is called "cerebral achromatopsia". People affected with cerebral achromatopsia are perfectly aware of their visual experiences; however, they are unable to imagine or remember colors. They see the world like a black & white television where everything is a shade of gray. They cannot chromatically order or discriminate hue but they can distinguish color contrasts like a normal person. 'Transient achromatopsia' is a temporary loss of colour vision caused by a short-lived vascular insufficiency in the occipital cortex.

How can I create a color blind friendly website?
Apart from its aesthetic appeal, seeing many different colors allows us to distinguish things in the world. However, remember that there are always colorblind people among your audience and readers. Actually, there could be more than TEN colorblind people per 250 people visiting your site. Then, we, the web community, must create an atmosphere which makes it easier for colorblind individuals to differentiate between text and background along with images! There are 2 ways that we can make information in pictures available to colorblind people:
1) The simplest way is to increase the red/green contrast in the images.
2) We can also convert the variations in red and green colors into variations in brightness and/or blue/yellow coloration.
One way to test your website for colorblind usability is by using these tools:
- Color blind Web Page Filter,
- Vischeck.
Each tool will show a copy of your web page as if it was seen as a select type of color vision deficiency.
Firefox also has a great add-on which allows webmasters to see color contrasts:
- Color Contrast Analyser Firefox Extension.