Color Blindness (Dyschromacy)

Color “blindness” is more correctly known as color “deficiency” or dyschromacy. It is the inability to see or identify certain colors of the visible light spectrum. Approximately 8% of the population have color difficulties (estimates range from 4-12%). This means that in a class of 25, one, and possibly more students, likely will have difficulty distinguishing colors. Most will be male (Males are 17 times more likely to be colorblind than females).

John Dalton (1766–1844) was an English chemist and physicist credited with the development of the modern atomic theory. He also discovered a particular type of color blindness known as “Daltonism.”

Dyschromacy is inherited and is caused by a gene on the “X” chromosome. Since it is a sex-linked recessive condition, a male with an affected “X” chromosome will inherit the condition (always inherited from the mother), while a female must be born with both “X” chromosomes affected (inherited from both parents). A female with only one affected “X” chromosome will not have the condition, but may pass the gene to one of her children.

Dyschromacy is caused by differences in the absorption rates of the cones on the retina of the eye. Some people have red-green deficiency (common) while others have blue-yellow deficiencies (rare). A red/green color deficiency means that reds and greens are more difficult to distinguish, and blue/yellow color deficiency means that blues and yellows are more difficult to distinguish.

Dyschromacy presents many challenges in the science classroom due to the common use of color-coding for diagrams, maps, charts, and graphs. It can also make distinguishing features of various structures difficult to observe.

How can teachers help?

General Strategies:

Acknowledge the disability as legitimate.
Never ask students with dyschromacy to “prove” their disability.
Talk to the student and parents. Ask how you can help.

Consider alternatives to color coding:

Use gray scales or B&W.
Use symbols or shapes (this can be in addition to using color codes: a red diamond for example).
Label the colors.
Consider not using the colors that cause difficulties.
Use Black on White instructional sheets.
Allow sketches as an alternative to color reproductions.
Advocate for early dyschromacy screening (Ishihara test).
Let the student(s) know (privately) that you will help if they would like to discuss color deficiency in class.
If you are colorblind, talk openly about it with your students.

Colorblindness Resources

Article: Seven tips for teachers with colorblind students (excellent suggestions)

Article: Advice for teachers of colour blind students

Tests for colorblindness:

Technical article from The Journal of Neuroscience on advances in color science