There are three main categories of color blindness, which break down into at least eight distinct subtypes. The three broad groups are red-green color blindness (by far the most common), blue-yellow color blindness, and complete color blindness. Each group contains subtypes based on whether a specific type of color-sensing cell in your eye is weakened or missing entirely.
Red-Green Color Blindness: Four Subtypes
Red-green color blindness accounts for the vast majority of cases and comes in four forms. The difference between them depends on which cone cell is affected and whether it’s malfunctioning or completely absent.
Deuteranomaly is the single most common form of color blindness. Your green-sensitive cone cells work, but they’re slightly “off-tune,” picking up light at the wrong wavelength. This makes reds, greens, and yellows look muddy or washed out, but the shift is often mild enough that some people don’t realize they have it. Deuteranomaly and related green-cone deficiencies affect up to 6% of males in some populations.
Deuteranopia is the more severe version. Rather than a weakened green cone, you’re missing it entirely. Your eye only has two functioning cone types instead of three, which collapses the red-green spectrum into shades of gold and blue.
Protanomaly involves a weakened red-sensitive cone. Red, orange, and yellow appear shifted toward green and look less vivid. Protan defects (protanomaly and protanopia combined) account for about 1% of males in European populations.
Protanopia means the red cone is absent altogether. Like deuteranopia, it reduces your vision to two cone types, but with a notable practical difference: because the red cone is gone, red lights and brake lights can appear especially dim or dark, which matters for driving.
Blue-Yellow Color Blindness: Two Subtypes
Blue-yellow color blindness involves the short-wavelength cone, the one responsible for detecting blue and violet light. It’s far rarer than the red-green types, affecting fewer than 1 in 10,000 people, and it hits men and women at equal rates because the gene sits on chromosome 7 rather than the X chromosome.
Tritanomaly means your blue cone is present but underperforming. Blues look greener, and it becomes hard to separate yellow from pink.
Tritanopia means the blue cone is missing. The world looks like variations of pink and teal. This is rare enough that many people who have it were never screened for it, since the most common color vision test (the Ishihara plate test) only checks for red-green deficiencies.
Complete Color Blindness: Two Forms
Complete color blindness, or monochromacy, means you see little to no color at all. It comes in two forms, both extremely rare and inherited equally by males and females.
Rod monochromacy (also called achromatopsia) is the total absence of functioning cone cells. Vision relies entirely on rod cells, which detect light and dark but not color. People with this condition see the world in shades of gray and typically have additional challenges: high sensitivity to bright light, involuntary eye movements, and reduced visual sharpness. Daily life often requires tinted lenses or filters to manage light sensitivity.
Cone monochromacy is slightly different. One single type of cone still works (usually the blue-sensitive one), alongside the rods. Color perception is still essentially absent because the brain needs input from at least two different cone types to compare wavelengths and create a sense of color. Vision tends to be somewhat better than in rod monochromacy, but the experience of a colorless world is similar.
Why Men Are Far More Likely to Be Color Blind
About 8% of men of Northern European descent have some form of red-green color blindness, compared to roughly 0.4–0.5% of women. The reason is straightforward genetics. The genes controlling red and green cone cells sit on the X chromosome. Men have one X chromosome, so a single copy of the gene variant is enough. Women have two X chromosomes, meaning both copies would need to carry the variant for color blindness to appear. If only one does, the other compensates.
This gap varies significantly across populations. Prevalence in men ranges from under 1% in Fijian populations to over 9% among Norwegians and Russians. Aboriginal Australian men show rates around 1.9%, Japanese men around 4%, and men in parts of India as high as 7.5%. Blue-yellow and complete color blindness don’t follow this pattern because their genes are on non-sex chromosomes, so they affect everyone equally.
How Color Blindness Is Diagnosed
The most familiar test is the Ishihara plate test, where you look at circles filled with colored dots and try to read a hidden number. It’s fast and effective at screening for red-green deficiencies, but it can’t classify the exact type or measure severity, and it misses blue-yellow deficiency entirely.
For a more precise diagnosis, the Farnsworth Panel D-15 test asks you to arrange colored discs in order. The pattern of errors reveals which type of color blindness you have. The Farnsworth-Munsell 100-hue test works similarly but with far more discs, giving a detailed picture of how subtle your deficiency is. The gold standard in clinical research is the anomaloscope, an instrument that asks you to match two colored lights. It’s the most accurate tool available, but it’s expensive and requires a trained examiner, so it’s mostly limited to research settings and occupational screening.
Occupational testing takes a different approach. Aviation authorities, railways, and maritime services use lantern tests that simulate real-world signal lights. Passing one of these tests matters more to employers than your exact diagnosis, because what they need to know is whether you can reliably distinguish a red signal from a green one in working conditions.
Inherited vs. Acquired Color Blindness
Most color blindness is genetic, present from birth, stable over a lifetime, and affecting both eyes equally. But color vision can also deteriorate later in life. Conditions that damage the optic nerve or retina, including glaucoma, macular degeneration, diabetic eye disease, and multiple sclerosis, can gradually erode color perception. Certain medications and chemical exposures can do the same. Acquired color blindness often affects one eye more than the other and may worsen over time, which distinguishes it from the inherited forms. It also tends to affect blue-yellow discrimination more than red-green, which is the opposite of the genetic pattern.
Age alone plays a role too. The lens of the eye yellows naturally over decades, which can subtly shift how blues and purples appear. This isn’t classified as color blindness in the clinical sense, but it’s a real change in color perception that many people notice in their 60s and beyond.