Colorblindness is usually an inherited condition that is X-linked recessive. As a result, very few women are colorblind, but approximately 1 in 10 men has some degree of colorblindness.

There are also some forms of colorblindness that can be acquired after birth. The most common of these is caused by a rheumatoid arthritis drug called hydroxychloroquine (Plaquenil).

The most common type of colorblindness is red-green, but there is a wide range of variability within this group from very mild to extreme. The second most common form is blue-yellow, and a red-green deficit is almost always associated with this form.

The most severe form of colorblindness is achromatopsia, the inability to see any color. It is often associated with other problems such as amblyopia (lazy eye), nystagmus, photosensitivity, and extremely poor vision.

People who are colorblind are not be able to see colors with the same intensity as most other people. However, the symptoms may be so mild that some patients are unaware they are colorblind unless specifically tested.

Most commonly, people have difficulty distinguishing shades of a particular color. Parents may notice colorblindness in a more severely affected child at the time the child would normally learn colors. In severe cases, other symptoms such as jiggling eyes (nystagmus) or roving eye movements may be present.