There are eight distinct types of color blindness, grouped into three main categories: red-green deficiency (four types), blue-yellow deficiency (two types), and total color blindness (two types). Red-green color blindness is by far the most common, affecting roughly 1 in 12 men and 1 in 200 women. The rarest forms involve a near-complete or total loss of color vision.
Red-Green Color Blindness: Four Types
Red-green deficiency accounts for the vast majority of color blindness cases. It comes in four subtypes, split into two pairs: the milder “anomaly” versions, where the relevant color-sensing cells work but are shifted in sensitivity, and the more severe versions, where those cells are missing entirely.
Deuteranomaly is the single most common type of color blindness. It shifts green perception toward red, making certain greens look muddier or more reddish. Most people with deuteranomaly describe it as mild, and it rarely interferes with everyday tasks.
Protanomaly works in the opposite direction. Certain reds appear more greenish and less bright. Like deuteranomaly, it’s generally mild and often goes unnoticed until someone takes a formal color vision test.
Deuteranopia and protanopia are the severe counterparts. In both cases, a person cannot distinguish red from green at all. Deuteranopia results from missing green-sensing cells, while protanopia results from missing red-sensing cells. The practical experience is similar for both: reds, greens, browns, and some oranges can look nearly identical.
Blue-Yellow Color Blindness: Two Types
Blue-yellow deficiency is far less common than red-green. It involves the short-wavelength (blue-sensing) cells in your eye rather than the red or green ones.
Tritanomaly is the milder version. Blue appears more greenish, and it can be harder to separate yellow from violet. Tritanopia is the severe form, where blue-sensing cells are absent. People with tritanopia lose the ability to distinguish blue from green and yellow from violet. The National Institutes of Health classifies tritanopia as an extremely rare condition caused by genetic mutations that can be inherited or arise spontaneously.
One important distinction: blue-yellow deficiency follows a different inheritance pattern than red-green types, which is why it affects men and women at roughly equal rates.
Total Color Blindness: Two Types
Complete or near-complete color blindness is the rarest category. Both forms involve a substantial loss of cone cell function (the cells responsible for color and sharp central vision) while the rod cells, which handle low-light and peripheral vision, still work.
Achromatopsia is true, total color blindness. People with achromatopsia see only in shades of gray. Because their cone cells don’t function, they also typically have reduced visual sharpness and significant sensitivity to bright light. At least five different genes can cause the condition.
Blue cone monochromacy is slightly less severe. One type of cone cell (the blue-sensing one) still works, so there is a very limited capacity for color perception. But because two of the three cone types are missing, functional color vision is extremely poor, and light sensitivity and reduced acuity are still major issues.
Why Men Are Affected Far More Often
The genes responsible for red-green color vision sit on the X chromosome. Men have only one X chromosome, so a single copy of a defective gene is enough to cause color blindness. Women have two X chromosomes, meaning both copies would need to carry the mutation for the condition to appear. This is why about 8% of men have some form of color deficiency while only about 0.5% of women do.
Blue-yellow deficiency and achromatopsia are controlled by genes on non-sex chromosomes, so they don’t show the same male-heavy pattern. These types are inherited in a way that requires both parents to carry the gene variant.
Color Blindness You Aren’t Born With
Not all color vision problems are genetic. A number of health conditions can damage color perception over time, including diabetes, macular degeneration, glaucoma, multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, sickle cell anemia, and chronic alcoholism. Certain medications can also affect color vision, including hydroxychloroquine, which is used to treat rheumatoid arthritis and other inflammatory conditions.
Acquired color deficiency tends to look different from the inherited kind. It often affects both eyes unequally, may worsen gradually, and can sometimes improve if the underlying cause is treated. Inherited color blindness, by contrast, is stable from birth and affects both eyes the same way.
How Color Blindness Is Tested
The most familiar screening tool is the Ishihara plate test, where you look at circles made of colored dots and try to identify a number hidden inside. It takes about two minutes and is good at catching red-green deficiency, with a sensitivity around 83% and near-perfect specificity. A computerized version performs even better, catching close to 100% of cases.
For a more detailed picture, especially when the type and severity need to be pinpointed, eye care professionals use the Farnsworth-Munsell 100 Hue test. You arrange 100 colored caps in order, and where you make errors reveals exactly which part of the color spectrum gives you trouble. The manual version takes about 15 minutes; an online adaptation cuts that roughly in half, though it tends to score slightly higher than the in-person version.
If you suspect you have color blindness but have never been formally tested, the Ishihara-style screening is a quick first step. A full hue-arrangement test can then clarify whether you’re dealing with a mild anomaly or a more significant deficiency, which matters for certain careers that require accurate color discrimination.