Colour blindness might not mean what you think. It actually has no relation to being blind and a very small number of people see the world entirely gray. Take the colour deficiency screening below and view examples of what colour blind or deficient individuals see.
Most people who are considered colour blind have a colour vision deficiency which means they can see colours, but they just see them a little differently. Colours may look faded or dull, or two different colours could look very similar. This happens because the cones in the eye are missing one or more of the light-sensitive pigments.1 Genetics are typically to blame, but sometimes age, diseases and medication can be the culprit.
The most widely used screening test for colour deficiencies is the Ishihara Colour Vision Test. The test contains circular patterns comprised of many dots of various colours, brightness and sizes. Within the circle is a number. A colour deficient person will either be unable to see the number or will see a different number than the one seen by a person with normal colour vision.2