Color vision deficiency, also commonly called color blindness, is an inability to distinguish one or more colors as seen by those with normal color vision and cannot be corrected with prescription eyeglasses. Color vision deficiency may take a variety of different forms, but the most common are red-green color deficiencies, in which a person has a hard time distinguishing color differences between objects that are red, yellow, or green. For example, such a person might have difficulty perceiving the difference between a red delicious apple and a (green) granny smith apple. Blue-yellow color deficiency is another common form of color blindness. Total color vision deficiency in which a person sees only in shades of gray is very rare. While these are some common types of color vision deficiency, there are many types of deficiencies in perceiving various color combinations.

Color vision deficiency can have a major impact on the every day activities of those who have the condition. For example, color blindness may make it difficult to interpret traffic signals, distinguish images on a computer screen, or interpret maps, charts, and other types of graphics in school and on the job. 

Some ways that the color blind adapt are by learning to distinguish other identifying characteristics of items besides color, for example, traffic signals can be judged based on positioning of the lights rather than their colors. In some cases, adaptive equipment can help people with color blindness navigate the world more easily.

For more information on color vision, see the links below:

1.  Information on genes that cause certain types of color vision deficiency.

National Institutes of Health – Genetic Color Vision Deficiency

2.  Information on all types of color vision deficiency, including those caused by chronic illnesses and exposure to environmental toxins.

American Optometric Association – Information on Causes of Color Vision Deficiency

3.  Fifty facts about color vision deficiency.

Color Vision Deficiency Facts

4.  Information on color vision deficiency in children.

Color Blindness in Children

5.  What parents, teachers, and school nurses should know about color blindness.

Color Blindness Information for Educators

6.  A series of images offered online as a screening tool for color vision deficiency.

Color Vision Deficiency Test

7.  A description of the different types of color blindness.

Types of Color Blindness

8.  A selection of photographs showing how those affected by different types of color blindness perceive color.

What a Color Blind Person Sees

9.  Color blindness information, including a magnified image of the rods and cones (light photoreceptor cells) in the eye.

Rods and Cones of the Eye

10.  Information on web design considerations for people with color vision deficiency.

Web Graphics for Color Vision Deficiency

11.  Information on achromatopsia, a rare form of total color blindness in which the world is perceived only in shades of gray.

Achromatopsia Information

12.  Information and resources on red-green color blindness, including symptoms, prevalence, treatment, and prognosis.

James Madison University – Red-Green Color Blindness

13.  Information on resources for adapting to color vision deficiency.

Resources for Adapting to Color Vision Deficiency

14.  Information on traffic safety and traffic signal colors for the color blind.

University of Michigan – Traffic Signals for People with Color Vision Deficiency

15.  Effects of colors on day-time cycling visibility for those with color vision deficiency.

Bicycle Safety Consideration for Color Vision Deficiency