Color vision
Color blindness Nine types, simulated
About 1 in 12 men and 1 in 200 women of European descent have some color vision deficiency, most of them red–green. These pages show what each type does to colors, which pairs it confuses, and how to design so it does not matter.
- Types here
- 9
- Most common
- Deuteranomaly
- Simulation
- Machado et al. (2009)
Live lab
Every type, side by side
Four everyday interfaces, or an image of your own, through all nine types at once. Drag the divider, change the severity, and turn on the fix to see the same interface designed so color is never the only clue.
The live lab needs JavaScript. The sections below show the same simulation, color by color.
A line chart of weekly sign-ups in four channels, told apart by color.
The same scene through all nine types, each at its usual severity.
- Closest pair
- Typical vision
- Deuteranomaly
- Verdict
ΔE2000 between the two key colors drawn closest together. Under 5 is too close for thin lines and small marks; 10 or more is safe at any size. A rule of thumb, not a standard.
With the fix, words, icons, numbers and patterns carry the meaning too, so the scene still reads even where two colors stay close.
A photo has no key colors to compare, so the lab simulates every pixel instead. Save the result to share it.
Dichromacy
One cone type missing
Two of the three cone types work, so every color has to be told apart with two signals instead of three. The first strip is twelve hues as typical vision sees them; each card is the same twelve as seen with that type.
Anomalous trichromacy
One cone type shifted
All three cone types work, but one responds to the wrong wavelengths. These are the milder forms, and the most common: deuteranomaly alone affects about 1 in 20 men of European descent.
Monochromacy
Little or no color
Rare conditions in which one cone type, or none, carries daylight vision. They usually come with reduced sharpness of vision and sensitivity to bright light.
How common
How common each type is
Red–green types are inherited on the X chromosome, so they are far more common in men; the rest affect men and women about equally. Deuteranomaly alone outnumbers all the others together.
- Protanopia
- Deuteranopia
- Tritanopia
- Protanomaly
- Deuteranomaly
- Tritanomaly
- Achromatopsia
- Achromatomaly
- Blue-cone monochromacy
People of European descent; the scale is logarithmic, each step ten times the last. Sharpe et al. 1999 · MedlinePlus: color vision deficiency · MedlinePlus: achromatopsia
Ancestry
Red–green deficiency by ancestry
It is most common in people of European descent and least common among Indigenous peoples of the Americas and the Pacific.
| Ancestry | Men | Women |
|---|---|---|
| European ancestry | 7.4% | 0.5% |
| Asian ancestry | 4.17% | 0.58% |
| African ancestry | 2.61% | 0.54% |
| Aboriginal Australians | 1.98% | 0.03% |
| Indigenous peoples of the Americas | 1.94% | 0.63% |
| Pacific Islanders | 0.82% | No data |
Red–green deficiency of every kind, from 67 studies collected in Table 1.5 of Sharpe et al. (1999). The groups are the source's, renamed. Sharpe et al. 1999
Confusion lines
Three axes of confusion
Every red–green type confuses colors along one family of lines, and every blue–yellow type along another. Point at a group of colors to see the line they share.
-
Protan: protanopia and protanomaly
Seen as one hue
The numbers are the closest pair in each group, typical vision first.
The lines meet at points worked out from the cone measurements of Smith and Pokorny; strictly those belong to a corrected version of this diagram, so the lines here are close, not exact. Smith & Pokorny 1975
- Confusion lines
- The line through white
- White (D65)
- Neutral point 494 nm
- sRGB gamut
-
Deutan: deuteranopia and deuteranomaly
Seen as one hue
The numbers are the closest pair in each group, typical vision first.
The lines meet at points worked out from the cone measurements of Smith and Pokorny; strictly those belong to a corrected version of this diagram, so the lines here are close, not exact. Smith & Pokorny 1975
- Confusion lines
- The line through white
- White (D65)
- Neutral point 500 nm
- sRGB gamut
-
Tritan: tritanopia and tritanomaly
Seen as one hue
The numbers are the closest pair in each group, typical vision first.
The lines meet at points worked out from the cone measurements of Smith and Pokorny; strictly those belong to a corrected version of this diagram, so the lines here are close, not exact. Smith & Pokorny 1975
- Confusion lines
- The line through white
- White (D65)
- Neutral point 566 nm
- sRGB gamut
Genes
The genes behind each type
Red–green types and blue-cone monochromacy come from the opsin genes on the X chromosome; tritan types from the S-opsin gene on chromosome 7; achromatopsia from genes the cones need to signal at all.
| Type | Genes | Where | Inheritance |
|---|---|---|---|
| Protanopia | OPN1LW | Xq28 | X-linked recessive |
| Deuteranopia | OPN1MW | Xq28 | X-linked recessive |
| Tritanopia | OPN1SW | 7q32.1 | Autosomal dominant |
| Protanomaly | OPN1LW, OPN1MW | Xq28 | X-linked recessive |
| Deuteranomaly | OPN1MW, OPN1LW | Xq28 | X-linked recessive |
| Tritanomaly | OPN1SW | 7q32.1 | Autosomal dominant |
| Achromatopsia | CNGB3, CNGA3, GNAT2, PDE6C, PDE6H, ATF6 | Six genes, among them CNGB3 at 8q21.3 and CNGA3 at 2q11.2 | Autosomal recessive |
| Achromatomaly | CNGA3, GNAT2, PDE6H | 2q11.2, 1p13.3 and 12p12.3 | Autosomal recessive |
| Blue-cone monochromacy | OPN1LW, OPN1MW | Xq28 | X-linked recessive |
Diagnosis
How color vision is tested
No one test does everything: plates screen, arrangement tests show the axis, and an anomaloscope classifies. Only an eye care professional can diagnose a color vision deficiency.
| Test | What it is | Red–green, dichromacy | Red–green, anomalous | Blue–yellow | Monochromacy |
|---|---|---|---|---|---|
| Ishihara plates | Plates of colored dots hiding numbers: the standard screen for red–green deficiency. It cannot grade severity or tell dichromats from anomalous trichromats. Ishihara instructions | Detects it | Detects it | Misses it | Not used |
| HRR plates | Plates with shapes instead of numbers. They screen for red–green and blue–yellow loss and grade it as mild, medium or strong. Bailey et al. 2004 | Detects and grades it | Detects and grades it | Detects and grades it | Not used |
| Farnsworth D-15 | Fifteen colored caps to put in order. Almost every dichromat fails; many people with a mild anomaly pass. The pattern of errors shows the axis. Birch 2008 | Detects it | Partly | Detects it | Detects it |
| Farnsworth–Munsell 100 Hue | Eighty-five caps in four trays, scored for errors. Good for measuring discrimination and following an acquired loss; weak at telling inherited types apart. Birch 1989 | Partly | Partly | Partly | Not used |
| Nagel anomaloscope | Match a yellow light with a mix of red and green. The reference test for red–green deficiency: it tells protan from deutan and dichromacy from anomalous trichromacy, and grades severity. Birch 2008 | Detects and grades it | Detects and grades it | Misses it | Partly |
| Moreland anomaloscope | A blue–green match for tritan defects. Its power is limited, because the eye's lens and macular pigment shift the match. Sharpe et al. 1999 | Not used | Not used | Partly | Not used |
| CAD test | A computer test that measures red–green and yellow–blue thresholds against moving luminance noise, and reports severity in standard units. Rodriguez-Carmona et al. 2012 | Detects and grades it | Detects and grades it | Detects and grades it | Not used |
| Cambridge Colour Test | A computer test: find the gap in a C drawn in colored dots among dots of random lightness. It measures thresholds along the protan, deutan and tritan axes. Regan et al. 1994 | Detects and grades it | Detects and grades it | Detects and grades it | Not used |
| ERG and genetic testing | An electroretinogram shows cone responses absent or much reduced, with rods near normal; a genetic test confirms the gene. Blue-cone monochromacy is told apart by its working S cones. GeneReviews: achromatopsia | Not used | Not used | Not used | Detects it |
Acquired
Color vision lost later in life
Not every deficiency is inherited. Disease, medicines and age can change color vision too, and unlike an inherited loss, an acquired one can affect one eye more than the other, or come and go.
Köllner's rule: a blue–yellow loss that starts later in life points to the eye's lens or outer retina; a red–green one points to the inner retina or the optic nerve. Lacerda et al. 2012
Glaucoma is the best-known exception: it damages the optic nerve, yet its color loss usually starts as blue–yellow. Costa et al. 2024
- Changes in the eye's lens, among them its yellowing with age Sharpe et al. 1999
- Glaucoma Sharpe et al. 1999
- Diabetes Sharpe et al. 1999
- Multiple sclerosis and other diseases of the optic nerve Sharpe et al. 1999
- Some medicines, such as chloroquine, and chemicals, such as organic solvents MedlinePlus: color vision deficiency
Your palette
Check your colors
Paste a palette, or start from one below. The bars show the closest pair under every type; the table shows every pair under the one you pick.
The checker needs JavaScript.
Hex codes, separated by commas or spaces, up to 12. Skipped:
Closest pair under each type
Too close Borderline Distinct
Method
How the simulations work
Dichromacy and anomalous trichromacy use the matrices of Machado, Oliveira and Fernandes (2009) in linear light, the anomalous types at severity 0.6. Achromatopsia keeps only luminance, and blue-cone monochromacy only the S-cone signal.
A simulation shows the loss of discrimination, not what any one person sees, which varies.
Simulate your own pageAchromatomaly has no published model, so its page is an illustration: each color mixed 60% of the way to its own gray.
Color pages show every color under the four full types, and the Tailwind family pages show each whole scale.