Color blindness is a condition where your eyes can’t distinguish certain colors the way most people do. It affects roughly 8% of men and 0.5% of women with Northern European ancestry, with lower rates in Asian and African populations. Despite the name, most people with color blindness aren’t seeing in black and white. They see colors, just a narrower or shifted range of them.
How Color Vision Works
Your retina contains two types of light-detecting cells: rods (for dim light) and cones (for color). There are three kinds of cone cells, each tuned to a different slice of the light spectrum. Short-wavelength (S) cones respond best to blue light, medium-wavelength (M) cones to green, and long-wavelength (L) cones to red. Your brain builds color perception by comparing the signals from all three cone types simultaneously.
Here’s what’s counterintuitive: each individual cone is actually color blind on its own. A single cone can only report how many photons it caught, not what color those photons were. A green cone hit by a lot of red light might fire the same way it would if hit by a little green light. Your brain resolves this ambiguity by comparing activity across cone types. If the red cones fire strongly but the green cones don’t, your brain registers “red.” When one cone type is missing, malfunctioning, or responding to the wrong wavelengths, these comparisons break down and certain colors become indistinguishable.
Red-Green Color Blindness
Red-green deficiency is by far the most common form. It comes in several varieties:
- Deuteranomaly: The most common type overall. The green-sensitive cones respond to slightly wrong wavelengths, making certain greens look more red.
- Protanomaly: The red-sensitive cones are shifted, making reds appear more green and less bright.
- Deuteranopia and protanopia: More severe forms where either the green or red cone type is completely nonfunctional. People with either of these can’t distinguish red from green at all.
In the milder forms (deuteranomaly and protanomaly), people still have three types of cones, but one type produces a pigment whose sensitivity overlaps too much with another. The brain still gets two different signals from the red-green range, but they’re so similar that telling certain shades apart becomes difficult or impossible. In the more severe forms, one cone type is missing entirely, collapsing three-channel color vision down to two.
Blue-Yellow and Total Color Blindness
Blue-yellow color blindness is much rarer. Tritanomaly makes it hard to distinguish blue from green and yellow from red. Tritanopia, the more severe version, blurs the boundaries between blue and green, purple and red, and yellow and pink, while also making colors appear less vivid overall.
Total color blindness, called achromatopsia, is rarer still, affecting about 1 in 30,000 to 50,000 people worldwide. People with this condition have no functioning cone cells and see entirely in shades of gray. It also comes with other significant vision problems: about 96% experience severe light sensitivity, roughly 94% have involuntary eye movements (nystagmus), and many have reduced visual sharpness and difficulty with glare. Unlike red-green or blue-yellow deficiency, which may go unnoticed for years, achromatopsia is usually identified in early childhood.
Why It’s Far More Common in Men
The genes for the red and green cone pigments sit right next to each other on the X chromosome. Because males have only one X chromosome, a single defective gene is enough to cause red-green color blindness. Females have two X chromosomes, so a working copy on one can compensate for a faulty copy on the other. A woman would need defective genes on both X chromosomes to be affected, which is far less likely. This is why red-green color blindness shows up in about 8% of men but only 0.5% of women.
The high degree of similarity between the red and green pigment genes also makes them prone to swapping segments during reproduction, which is why red-green deficiency is so much more common than other forms. The blue cone pigment gene sits on a completely different chromosome (chromosome 7), and blue-yellow deficiency follows a different inheritance pattern, affecting men and women at similar rates.
Color Blindness That Develops Later in Life
Not all color vision problems are inherited. Damage to the eyes or brain can cause color blindness to develop at any age. Common causes include eye diseases like glaucoma and age-related macular degeneration, neurological conditions like Alzheimer’s disease and multiple sclerosis, certain medications (including some used for rheumatoid arthritis), and eye or brain injuries such as retinal detachment or tumors. Color vision also tends to decline naturally with aging, particularly if cataracts develop.
Acquired color vision loss can affect one or both eyes and may worsen over time, unlike inherited forms which remain stable throughout life. If you notice a change in how you perceive colors as an adult, that’s worth mentioning to an eye care provider since it can sometimes be an early sign of another condition.
Living and Working With Color Blindness
Most people with color blindness adapt without major difficulty, but the condition does create real friction in daily life. Picking out ripe fruit, reading color-coded charts, matching clothes, interpreting traffic lights by position rather than color, and struggling with certain video games or maps are common experiences.
Specialty glasses with spectral notch filters (such as EnChroma lenses) can help people with mild to moderate red-green deficiency. A study from UC Davis Eye Center found that these filters increase the separation between color channels, helping users see colors more vibrantly and distinctly. The effects improved over two weeks of regular use. These glasses don’t restore normal color vision, but they can make previously indistinguishable shades easier to tell apart. Software-based solutions like color filters on phones, computers, and gaming consoles can also remap problem colors into distinguishable ones.
Certain careers do impose color vision requirements. Military service, commercial aviation, rail transport, law enforcement, and some medical specialties either restrict or test for adequate color vision. About 24% of people with color blindness report being barred from a specific occupation because of it. Some of these restrictions have loosened over time. The U.K.’s Civil Aviation Authority introduced updated testing criteria in 2009 that allowed 30 to 35% more applicants with color vision deficiency to qualify as pilots. New Zealand followed in 2019 with a practical competency test that evaluates real-world performance rather than relying solely on chart-based screening. Notably, most of these professions prohibit the use of color-correcting lenses during testing or on the job, so specialty glasses aren’t a workaround for occupational requirements.
There are also safety considerations for driving. People with protanopia (missing red cones) perceive red lights as dimmer than normal, which can reduce reaction time at traffic signals. Some countries recommend against commercial driving licenses for people with this specific type.