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Types of Color Blindness

Color blindness is not one condition. The retina carries three cone types — long-wave (L, red), medium-wave (M, green), and short-wave (S, blue). Which cone is affected, and whether it is missing or merely shifted, determines the type.

The seven types below are grouped along three axes. Each card opens the full guide for that type — symptoms, confused colors, genetics, diagnosis, and day-to-day strategies.

Red-Green Axis (Most Common)

These account for the overwhelming majority of cases — roughly 8% of men and 0.5% of women. The genes involved sit on the X chromosome, which is why men are affected far more often. The four below run from mildest to most severe.

Deuteranomaly

Green-Weak

~5% of males

The most common type of all. M-cones are present but spectrally shifted toward the L-cones, so greens, yellows, and reds separate less cleanly. Often mild enough to go unnoticed for a lifetime.

Deuteranopia

Green-Blind

~1% of males

M-cones are absent entirely. Greens, yellows, and reds collapse toward a common muddy band — but unlike protan types, red brightness stays normal.

Protanomaly

Red-Weak

~1% of males

L-cones are present but shifted toward the M-cones. Carries the protan signature of reduced red brightness, which makes red signals and brake lights harder to pick out at a distance.

Protanopia

Red-Blind

~1% of males

L-cones are absent. Reds appear dark and muddy rather than merely shifted — the strongest brightness loss of any type, with real implications for traffic and warning signals.

Blue-Yellow Axis (Rare, Sexes Equal)

Far rarer than the red-green axis, with two key differences: the gene sits on chromosome 7 and is inherited autosomally, so men and women are affected equally; and acquired cases (glaucoma, diabetes, aging, medication) outnumber congenital ones — which is why a sudden decline in blue-yellow discrimination warrants an eye exam.

Tritanomaly

Blue-Weak

<1%, sexes equal

S-cones present but spectrally shifted. Inherited autosomally, so it affects men and women alike — and it is more often acquired than congenital.

Tritanopia

Blue-Blind

<0.01%, sexes equal

S-cones absent. Blues drift toward green and yellows toward pink or grey. Frequently acquired through glaucoma, diabetic retinopathy, or age-related lens changes.

Total Color Blindness (A Different Category)

The six types above all involve one cone class failing while the others keep working — a shift in discrimination. Achromatopsia is different: cone function collapses altogether and vision falls back on the rods, which is why it always comes with photophobia, nystagmus, and reduced acuity rather than color loss alone.

Achromatopsia

Monochromat

~1 in 30,000

Categorically different from the others: all or nearly all cones fail, leaving rod-based vision in shades of grey. Comes with photophobia, nystagmus, and low visual acuity — and is autosomal, not X-linked.

Reading the Names: -opia vs -anomaly

The root names the affected cone — prot- (L-cone, red), deuter- (M-cone, green), trit- (S-cone, blue). The suffix marks severity.

  • -opia（blindness) — that cone type is absent or non-functional, leaving two working cone types: dichromacy.
  • -anomaly（weakness) — the cone is present but its peak sensitivity is shifted; all three types still work with reduced separation: anomalous trichromacy. Severity runs on a continuum.

Which Test Should You Take?

Frequently Asked Questions

Clinically there are seven commonly described types, grouped along three axes. The red-green axis holds four of them — protanopia and protanomaly (L-cone), deuteranopia and deuteranomaly (M-cone). The blue-yellow axis holds tritanopia and tritanomaly (S-cone). Achromatopsia stands apart as total color blindness. Red-green types account for the overwhelming majority of cases.
The suffix marks severity. An -opia (protanopia, deuteranopia, tritanopia) means that cone type is absent or non-functional, leaving only two working cone types — dichromacy. An -anomaly (protanomaly, deuteranomaly, tritanomaly) means the cone is present but its peak sensitivity is shifted, so all three cone types still work with reduced separation — anomalous trichromacy. Anomalies span a continuous range from barely noticeable to nearly as severe as the matching -opia.
Deuteranomaly, the green-weak form, is the most common single type — it affects roughly 5% of men. Because it is a mild anomaly rather than a complete deficiency, many people who have it never realize it. Red-green deficiencies as a whole affect about 8% of men and 0.5% of women.
The genes for L-cone and M-cone photopigments (OPN1LW and OPN1MW) sit on the X chromosome. Men have one X, so a single altered copy produces the deficiency. Women have two X chromosomes and would generally need both copies altered. This is why red-green types are strongly male-skewed. The blue-yellow types are the exception: OPN1SW sits on chromosome 7 and is inherited autosomally, so tritan deficiencies affect men and women equally.
Start with an Ishihara-style plate test — it screens the red-green axis, which covers most cases. Standard Ishihara plates do not reliably detect blue-yellow deficiency, so if you suspect a tritan type, use a dedicated blue-yellow test or an arrangement test such as the D-15 or the Farnsworth-Munsell 100 Hue. Arrangement tests are also what grade severity, which plate tests cannot do well.
Inherited red-green and inherited blue-yellow deficiencies arise from genes on different chromosomes, so having both congenitally is very rare. However, acquired color vision loss can be layered on top of an inherited deficiency — for example, someone with congenital deuteranomaly who later develops a tritan-like defect from diabetic retinopathy or glaucoma. A sudden change in color perception always warrants an eye exam.

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