Color blindness has three main types: red-green, blue-yellow, and complete. Red-green is most common; blue-yellow and complete color blindness are rare.
Severity varies within each type.
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Types of Color Blindness
Short answer
There are three broad types of color blindness, grouped by which cone is affected: red-green (the most common by far), blue-yellow (rare), and complete color blindness (very rare). Red-green color vision deficiency splits into four named forms — protanomaly, protanopia, deuteranomaly, and deuteranopia — and affects about 1 in 12 men and 1 in 200 women. Each type also comes in degrees, from a mild anomaly to a full absence of one cone.
"Color blindness" almost never means seeing no color at all. It is an umbrella term for color vision deficiency (CVD): one of the eye's three cone types is missing or shifted, so certain colors are harder to tell apart. Which cone is affected decides the type, and how affected it is decides the degree. Below is every main type, what it confuses, and how common it is.
Types of color blindness at a glance
Grouped by the cone affected. Prevalence figures are approximate and vary by population.
| Type | Cone affected | Degree | What's confused | How common |
|---|---|---|---|---|
| Red-green | ||||
| Deuteranomaly | M (green), shifted | Anomalous (mild–moderate) | Greens with reds/browns; the most common form | ~6% of men |
| Deuteranopia | M (green), absent | Dichromat (severe) | Reds, greens, browns and some greys | ~1% of men |
| Protanomaly | L (red), shifted | Anomalous (mild–moderate) | Reds look duller/darker; red–green | ~1% of men |
| Protanopia | L (red), absent | Dichromat (severe) | Red–green; reds appear very dark | ~1% of men |
| Blue-yellow | ||||
| Tritanomaly | S (blue), shifted | Anomalous | Blue–green and yellow–pink | Very rare (<0.01%) |
| Tritanopia | S (blue), absent | Dichromat | Blue–green, purple–red, yellow–pink | Very rare (~1 in 10,000) |
| Complete | ||||
| Achromatopsia (monochromacy) | Two or three cones non-working | Complete | Little or no color; often light-sensitive | Very rare (~1 in 33,000) |
Red-green color blindness (protan and deutan)
Red-green is by far the most common color vision deficiency, affecting roughly 1 in 12 men and 1 in 200 women. It comes from a problem with either the L-cone ("red", the protan types) or the M-cone ("green", the deutan types), whose sensitivities overlap heavily — so a fault in either makes reds, greens, oranges and browns hard to separate.
Each side has two forms. An anomalous trichromat still has all three cones, but one is shifted, giving a mild-to-moderate weakness: protanomaly (red-weak) or deuteranomaly (green-weak). A dichromat is missing that cone entirely, a more severe form: protanopia or deuteranopia. Deuteranomaly is the single most common type of all.
Protan and deutan differ in a telling way: protans also see reds as darker and dimmer, because the L-cone contributes most of our sense of brightness in red light. Deutans usually keep normal brightness perception.
Blue-yellow color blindness (tritan)
Blue-yellow deficiency involves the S-cone ("blue"). It is far rarer than red-green and, unlike red-green, affects men and women about equally because the gene involved is not on the X chromosome. Tritanomaly is the shifted, milder form; tritanopia is the absent-cone form.
People with a tritan type tend to confuse blue with green and yellow with pink or violet. Because blue-cone signals are weak even in normal vision, blue-yellow results are also the hardest to judge reliably on an uncalibrated screen.
Complete color blindness (monochromacy)
True total color blindness — seeing the world only in shades of grey — is very rare. Achromatopsia (rod or cone monochromacy) means two or all three cone types do not work, so there is little or no color perception. It is usually present from birth and often comes with light sensitivity (photophobia) and reduced sharpness of vision, because it reflects how the retina itself is built.
Degrees: anomalous trichromacy vs dichromacy
Within a type, severity runs on a scale. Anomalous trichromats have a shifted cone and a milder deficiency that ranges from barely noticeable to fairly strong. Dichromats are missing one cone outright and have the more pronounced form. This is why two people described as "deutan" can have very different real-world experiences.
Most color blindness is inherited and present from birth, carried on the X chromosome — which is why red-green types are so much more common in men. Color vision can also change later in life from eye disease, diabetes, or some medications (acquired CVD), and acquired cases are more often blue-yellow.
How the type is identified
Screening — whether a deficiency is present — uses pseudo-isochromatic plates such as the Ishihara test, where a figure is hidden in colored dots that only certain cones can separate. Estimating the type (protan, deutan, or tritan) and degree uses arrangement tests like the Farnsworth D-15 and, in clinics, an anomaloscope or computer-based test (e.g. CAD).
An online screening is a useful first check and is reliable for catching moderate-to-strong deficiencies, but type and degree are best read as estimates — mild cases especially can be misclassified between red and green, and no uncalibrated screen can replace an eye-care professional.
Want to know your type?
Take a free screening. The color blind test estimates your type (protan, deutan, or tritan) and degree in about two minutes, or try the Ishihara test for a quick red-green check.
Types of color blindness — frequently asked questions
- What are the three main types of color blindness?
- Red-green (the most common, from the L- or M-cone — protanomaly, protanopia, deuteranomaly, deuteranopia), blue-yellow (rare, from the S-cone — tritanomaly, tritanopia), and complete color blindness or monochromacy (very rare, seeing little or no color).
- What is the most common type of color blindness?
- Deuteranomaly — a shifted green (M) cone giving a mild-to-moderate red-green weakness. Red-green deficiency overall affects about 1 in 12 men and 1 in 200 women.
- What is the difference between protan and deutan?
- Both are red-green types. Protan affects the L- ("red") cone and also makes reds look darker and dimmer; deutan affects the M- ("green") cone and usually keeps normal brightness. Each comes in a milder anomalous form and a more severe dichromat form.
- What is the rarest type of color blindness?
- Complete color blindness (achromatopsia) is the rarest, at roughly 1 in 33,000. Blue-yellow (tritan) deficiency is also rare compared with red-green.
- Can you tell which type you have from an online test?
- A good online screening can reliably flag whether a moderate-to-strong deficiency is present and give an estimate of type and degree. Treat the type as an estimate — mild red and green are easy to mix up, and confirming the exact type and degree needs an eye-care professional.
- How many kinds of color blindness are there?
- Eight named forms, grouped into three families. Red-green covers protanomaly, protanopia, deuteranomaly and deuteranopia; blue-yellow covers tritanomaly and tritanopia; and complete colour blindness covers rod monochromacy (achromatopsia) and cone monochromacy. Red-green accounts for nearly all cases.
- What are the different kinds of color blindness?
- Anomalous trichromacy, where one cone pigment is shifted and produces a milder deficiency; dichromacy, where one cone type is absent and the deficiency is strong; and monochromacy, where colour vision is largely or entirely absent. Each named form is one of those three patterns applied to a specific cone.
- What are the 7 types of color blindness?
- Lists vary because complete colour blindness is sometimes counted as one category and sometimes as two. The usual seven are protanomaly, protanopia, deuteranomaly, deuteranopia, tritanomaly, tritanopia and achromatopsia; adding cone monochromacy separately makes eight.
- Are 'colour blindness' and 'color blindness' the same thing?
- Yes — 'colour blindness' is the British spelling and 'color blindness' the American one; the condition, the types (protan, deutan, tritan), and the tests are identical. UK sources such as the NHS also use the clinical term 'colour vision deficiency' (CVD), which covers the same set of conditions described on this page.
Go deeper on each type
Red-green color blindness
The family that covers roughly 99% of cases, and what it confuses.
Deutan color blindness
Deuteranomaly and deuteranopia — the single most common form.
Protan vs deutan
How to tell the two red-green types apart, and why it matters.
Blue-yellow (tritan)
The rare axis that plate tests routinely miss.
Sources
- National Eye Institute (NEI) — Types of Color Blindness
- NHS — Colour vision deficiency (colour blindness)
- American Academy of Ophthalmology — What Is Color Blindness?
- Colour Blind Awareness — Types of colour blindness
Last reviewed July 26, 2026. Informational only and regularly reviewed — not a substitute for advice from an eye-care professional.