For most people with color blindness, the world isn’t black and white. It’s a full, vivid scene where certain colors collapse into each other, making reds and greens, or blues and yellows, look like the same shade. About 8% of men and 0.5% of women of Northern European descent have some form of red-green color blindness, making it far more common than most people realize. What they see depends on which type they have.
Red-Green Color Blindness: The Most Common Type
Red-green color blindness comes in two main forms, called protanopia and deuteranopia. Both make it impossible to tell the difference between red and green, but they get there differently. In protanopia, reds appear much darker and can look almost brown or black, while greens shift toward a dull yellow. In deuteranopia, reds and greens both slide toward a muddy brownish-yellow range. Either way, a red apple sitting on a green tree doesn’t pop out the way it does for someone with typical vision. The apple and the leaves can look nearly the same color.
Most people with red-green color blindness aren’t fully “blind” to those colors. Many have a milder version where their red-sensitive or green-sensitive cells work, just not well. They can see some distinction between red and green, but the colors look washed out and far more similar than they should. A traffic light, for instance, doesn’t display three crisp, obviously different colors. The red and green lights can look almost identical. Colorblind drivers learn to rely on position instead: red is always on top (or on the left in horizontal signals), yellow in the middle, green on the bottom or right.
Blue-Yellow Color Blindness
A much rarer type, called tritanopia, affects fewer than 0.01% of people and hits both sexes equally. This one scrambles a different set of colors entirely. People with tritanopia can’t distinguish blue from green, purple from red, or yellow from pink. Blues tend to look greenish, and yellows can appear pinkish or even light gray. The sky and a grassy field might look strikingly similar. Because blue-yellow deficiency is so uncommon, it often goes undiagnosed for years.
Total Color Blindness
Complete color blindness, called achromatopsia, is the version most people imagine when they hear “colorblind,” but it’s extremely rare. People with this condition see the world entirely in shades of gray, like a black-and-white photograph. It also comes with other significant visual problems: extreme sensitivity to light and glare, involuntary eye movements, and significantly reduced sharpness of vision. Bright environments can be physically painful. This isn’t just a color issue; it fundamentally changes how someone navigates the visual world.
Why It Happens
Your retina contains three types of cone cells, each tuned to absorb a different range of light wavelengths. One type responds most to long wavelengths (reds), another to medium wavelengths (greens), and the third to short wavelengths (blues). Your brain mixes the signals from all three to produce the full color spectrum. Color blindness happens when one type of cone is missing or doesn’t function properly. In someone with deuteranopia, for example, the medium-wavelength cones are absent entirely. Researchers have confirmed this by measuring individual cone responses in living eyes: a person with deuteranopia shows only two response groups where a color-normal person shows three.
Red-green color blindness is passed down through the X chromosome, which explains the dramatic gap between men and women. Men have only one X chromosome, so a single copy of the gene is enough to cause the condition. Women have two X chromosomes, meaning both copies would need to carry the gene for color blindness to appear. That’s far less likely. A woman can carry the gene without being affected and pass it to her sons, which is why color blindness often seems to skip a generation.
Not all color vision loss is inherited. Eye diseases affecting the retina or optic nerve, certain medications (including some used to treat malaria), and exposure to industrial chemicals like organic solvents can all damage color perception later in life. Age-related changes in the lens of the eye can also shift how colors appear over time.
What Daily Life Actually Looks Like
The practical challenges go well beyond mixing up crayons. One of the most common frustrations is food. Roughly 41% of people with one type of red-green deficiency report difficulty judging whether fruit is ripe, and about a third struggle to tell whether meat is cooked or still raw. The color cues most people rely on without thinking, like a banana shifting from green to yellow or a steak going from red to brown, simply don’t register the same way. Some colorblind children become picky eaters because vegetables appear in unappealing, murky colors.
Work and school create another layer of difficulty. Pie charts, heat maps, color-coded graphs, and maps with colored boundary lines can be nearly impossible to read. A presentation that uses red and green to distinguish two data sets is, for someone with red-green deficiency, a chart with one color. Reading subway maps, interpreting weather radar, or following color-coded wiring diagrams all become tasks that require workarounds rather than a quick glance.
Choosing clothing, identifying bird species, picking matching paint colors, reading LED indicator lights on electronics: the list of small daily moments where color carries information is longer than most people with normal vision ever consider.
How It’s Diagnosed
The most familiar screening tool is the Ishihara test, a series of plates covered in colored dots with a number or shape hidden inside. If you can’t see the number, it suggests a red-green deficiency. Clinical versions use between 8 and 34 plates, while screening versions for children use around 12. The Ishihara test only catches red-green deficiency, though. Detecting blue-yellow problems requires a different computer-based test that checks across both color axes.
Do Corrective Glasses Work?
Color-correcting glasses, like those made by EnChroma, use specially designed filters that block a narrow slice of light wavelengths right where the red and green cone sensitivities overlap. By removing that overlapping light, the glasses push the remaining red and green signals further apart, making the contrast between those colors more noticeable. For someone whose cones work but overlap too much (the milder form of color deficiency), EnChroma glasses are predicted to increase red-green contrast by about 10%.
There’s an important catch. These glasses are designed for people who still have all three types of cones but whose red and green cones are too similar. If a cone type is missing entirely, as in full protanopia or deuteranopia, the glasses have little to no effect because there’s no signal to sharpen. The viral videos of people bursting into tears while trying these glasses represent real experiences for some users, but the results are inconsistent and depend heavily on the specific type and severity of deficiency. The glasses also don’t restore normal color vision. They shift and enhance certain contrasts, which can make the world look noticeably different, but the wearer still isn’t seeing what a color-normal person sees.