About 1 in 12 men and 1 in 200 women are color blind. See how common each type is, why it mostly skips women, and what DNA from John Dalton's eye revealed.
Published October 24, 2026
About 1 in 12 men (8%) and 1 in 200 women (0.5%) are color blind, according to figures for people of Northern European ancestry, where it is most common. Nearly all of them have an inherited red-green type, and the most common one, deuteranomaly, is mild enough that many people only find out from a test. It is rarer in people of East Asian and African ancestry, and the blue-yellow and complete forms are rare everywhere.
Color blindness almost never means seeing in black and white. The retina has three types of cone cells, tuned to long (red), medium (green) and short (blue) wavelengths. When one type is missing or shifted, some colors that look different to most people look the same.
30 color pairs: say same or different, and see which color ranges trip you up.
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Colour Blind Awareness, a UK charity, splits the 8% of color blind men into four red-green types. Deuteranomaly alone accounts for more than half of them.
Shares of men of Northern European ancestry, from Colour Blind Awareness, read on October 24, 2026. The four red-green types add up to the 8% figure, and they affect about 0.5% of women. Tritan types and achromatopsia are not carried on the X chromosome, so they hit men and women alike: together, perhaps 1 in 30,000 to 50,000 people.
The names follow a pattern. Protan types involve the red cones, deutan types the green cones and tritan types the blue cones. An -anomaly still has all three cone types, with two of them tuned too close together, so color vision ranges from almost normal to quite weak. An -opia has only two. Protans also see red as darker than other people do, which is why a dark red can pass for black.
The genes for the red and green cone pigments, OPN1LW and OPN1MW, sit side by side on the X chromosome. Men have a single X, inherited from their mother, so one faulty copy is enough. Women have two, and one working copy covers for the other.
The arithmetic explains the gap almost exactly. Since men have one X, the shares above are also the shares of X chromosomes that carry each defect: about 6% carry a deutan (green) defect and 2% a protan (red) one. A woman is color blind only if both her X chromosomes carry the same kind: 6% × 6% + 2% × 2% = 0.4%, right in line with the 0.4% to 0.5% that surveys find. A woman with one protan X and one deutan X sees colors normally, because each chromosome supplies the pigment the other lacks.
It also means far more women carry the trait than have it. Roughly 15% of women of European ancestry carry a red-green gene on one X, and each of their sons has a 1 in 2 chance of inheriting it. That is why color blindness seems to skip a generation, from a color blind grandfather, through his daughter, to her son.
Blue-yellow color blindness works differently. Its gene, OPN1SW, sits on chromosome 7, so it is as common in women as in men.
The 8% figure is a European one. In a 2012 review of studies from around the world, vision scientist Jennifer Birch put red-green color blindness at about 8% of European men and 0.4% of European women, against 4% to 6.5% of Chinese and Japanese men. A US study that tested children from four groups with the same method shows the gap:
From the Multi-Ethnic Pediatric Eye Disease Study (Xie and colleagues, Ophthalmology, 2014): 4,005 children aged 3 to 6 in Los Angeles and Riverside Counties, California. Young children are harder to test than adults, which may explain why white boys come out below 8%. Only 4 girls tested color blind, too few to compare groups.
In the autumn of 1792, the English chemist John Dalton, later famous for atomic theory, noticed that a pink geranium looked "almost an exact sky-blue" to him by day and red by candlelight. His friends saw no change at all. Only his brother saw what he saw.
On October 31, 1794, Dalton described his color vision to the Manchester Literary and Philosophical Society, the first scientific account of color blindness, later printed as Extraordinary Facts Relating to the Vision of Colours. He guessed that the fluid inside his eyes was tinted blue and filtered out red light, and he asked for his eyes to be examined after his death. When he died in 1844, they were: the fluid was perfectly clear.
His eyes were preserved, and in 1995 a team including Cambridge vision scientist John Mollon extracted DNA from them. The result, published in Science, overturned two centuries of guesswork: most experts had read Dalton's account as a lack of red cones, but he was missing the gene for the green pigment. Dalton was a deuteranope. Many languages still call color blindness after him: daltonisme in French, daltonismo in Spanish and Italian.
On the night of November 14, 1875, two express trains collided head-on at Lagerlunda, in Sweden. Uppsala professor Frithiof Holmgren suspected that the engine driver or his oiler had misread a signal because they were color blind. Neither survived to be tested, so Holmgren screened 266 workers on the Uppsala–Gävle line with his wool-matching test and found more than a dozen who were. Sweden made color vision testing mandatory for railway and shipping workers, and railroads across Europe and North America followed.
The twist came in 2012. After going back through the trial records, John Mollon and Lillie Cavonius concluded in Survey of Ophthalmology that the crash cannot be blamed on color blindness alone, and that Holmgren had won over the railway with a staged demonstration and some deception.
The test most people know came later. Japanese ophthalmologist Shinobu Ishihara published his dotted plates in 1917, designed while he held a military post. The full Ishihara test has 38 plates, and it is still the standard screen for red-green color blindness. It is not built to catch the blue-yellow types.
Complete color blindness, or achromatopsia, affects about 1 in 33,000 people. With no working cones, they see through rods alone, the cells built for night vision: the world comes in shades of gray, fine detail is blurry and daylight is dazzling.
On Pingelap, a coral atoll in Micronesia, almost 10% of people have it, and about 30% more carry the gene. Around 1775, a typhoon left only about 20 survivors on the island, and the ruler at the time is believed to have been a carrier. As the island grew back from so few people, a rare recessive gene became common. The neurologist Oliver Sacks visited and wrote about it in The Island of the Colorblind.
A woman who carries an -anomaly gene makes a shifted cone pigment from one X chromosome and a normal one from the other. In theory, that gives her four cone types instead of three, and an extra dimension of color: tetrachromacy.
In 2010, Gabriele Jordan, John Mollon and colleagues put that to the test with 24 women who carried deuteranomaly. In the Journal of Vision, they reported that only one, known as cDa29, behaved like a true tetrachromat on every test, telling apart color mixtures that look identical to everyone else. The other 23 saw colors like anyone else, extra pigment or not.
Not the inherited kind. According to the US National Eye Institute (NEI), most people adapt to it. Special glasses and contact lenses can make some colors easier to tell apart by increasing the contrast between them, and phone apps can name the colors in a photo, but none of them brings back the missing cone.
Gene therapy has worked in monkeys. Male squirrel monkeys are born red-green color blind, and in 2009, Katherine Mancuso, Jay and Maureen Neitz and colleagues injected a human red-pigment gene into the retinas of two adults. Months later, both passed a color test they had always failed. The study was published in Nature, and one of the two monkeys was named Dalton.
Color vision can also change later in life. The NEI lists cataracts, diabetes, multiple sclerosis, Alzheimer's disease, eye injuries and some medicines among the causes of acquired color vision loss. Unlike the inherited kind, it can get worse over time, so a change in how colors look is worth raising with an eye doctor.
The HumanRank color blindness test shows you 30 pairs of color panels, one at a time, and you answer Same or Different. 24 pairs differ slightly and 6 are identical, which catches guessing. The pairs cover red-green, blue-yellow, brightness and saturation, pale colors and low contrast, and the result shows which range gave you the most trouble.
Turn off night mode and blue-light filters, set a normal brightness and avoid colored room lighting before you start. A screen test depends on the display, so it is a quick check, not a diagnosis: an eye doctor can confirm a result with Ishihara plates or an anomaloscope. While you are checking your senses, the hearing test finds the highest pitch you can still hear, and our guide on why we lose our hearing with age explains why that number drops.
Find out which color ranges are hardest for you to separate.
About 1 in 12 men (8%) and 1 in 200 women (0.5%) of Northern European ancestry have red-green color blindness. It is less common in other populations, around 4% to 6.5% of Chinese and Japanese men and lower still in people of African ancestry. Blue-yellow and complete color blindness are rare, under 1 in 30,000 people.
Yes, but rarely: about 0.5% of women of European ancestry, against 8% of men. A woman needs the same kind of faulty gene on both X chromosomes, while a man has a single X. About 15% of women carry a red-green gene without being color blind themselves.
Deuteranomaly, a mild red-green type where the green cones are shifted toward red. It affects about 5% of men, more than half of all color blind men.
The red and green pigment genes are on the X chromosome. Men have one X, so a single faulty copy makes them color blind. Women have two, and a working copy on the second X makes up for a faulty one.
The English chemist John Dalton gave the first scientific account of it, his own, in 1794. That is why color blindness is called daltonism in many languages. A DNA test on his preserved eyes in 1995 showed he was a deuteranope, missing the green pigment gene.
Almost never. Most color blind people see plenty of colors but confuse certain ones, usually reds, greens, browns and oranges. Seeing only shades of gray, called achromatopsia, affects about 1 in 33,000 people.
Not the inherited kind. Special glasses can increase contrast between some colors, but they do not restore the missing cones. Gene therapy gave red-green color vision to two color blind monkeys in 2009, but there is no such treatment for people yet.
