Color blindness usually means confusing certain colors, not seeing in grey. It varies by type and severity, and several popular claims about human and animal vision are myths.
12 Genuinely Interesting Facts About Color Blindness
Short answer
Colour blindness almost never means seeing in grey — it means specific colour pairs stop being separable. It affects about 1 in 12 men and 1 in 200 women because the relevant genes sit on the X chromosome. Most mammals, including dogs, cats and cattle, are naturally in roughly the same position as a red-green colour blind human. And a few of the best-known facts about it, including the one about bulls and red capes, are wrong.
Reviewed July 26, 2026
Facts about what colour blind people actually see
One: almost nobody with colour blindness sees in greyscale. Total colour blindness, achromatopsia, affects roughly 1 in 30,000 people. Everyone else sees a full, saturated world with one axis compressed.
Two: the most common form is mild. Deuteranomaly, a shifted green cone, accounts for the majority of all cases, and plenty of people who have it reach adulthood without knowing.
Three: the confusions are specific, not general. Green with brown, red with brown, blue with purple, pink with grey. Blues and yellows usually look completely normal — often unusually vivid, because there is nothing competing with them.
Four: dim light makes it much worse. Colour discrimination depends on cone signals, and cones need light. Sorting laundry at night is genuinely harder than the same task in daylight.
Facts about the genetics
Five: it is inherited from the mother, for the common red-green forms. The cone pigment genes sit on the X chromosome, and a son's only X comes from her — which is why the trait appears to skip from grandfather to grandson through a carrier daughter.
Six: about 1 in 12 women is a carrier without being colour blind herself. That is the same rate as affected men, and it is why the condition is so much more widespread in families than it looks.
Seven: some carriers may have four cone types rather than three. Having two different versions of a cone pigment gene raises the possibility of functional tetrachromacy. Whether it produces measurably better colour discrimination is still debated, and the evidence is much thinner than popular articles suggest.
Eight: blue-yellow deficiency does not follow this pattern at all. Its gene is on chromosome 7, not the X, so it is inherited in an autosomal dominant pattern and affects men and women about equally.
Facts about animals — and one famous myth
Nine: most mammals are naturally in roughly the same position as a red-green colour blind human. Dogs, cats, horses, deer, cattle and rabbits all have two cone types instead of three. Trichromatic primates are the unusual ones.
Ten: bulls are not angered by red. Cattle are dichromats and do not see red as red at all — it is the movement of the cape that provokes the charge. The same cape moved the same way in any colour gets the same reaction.
Eleven: birds see more colours than we do, not fewer. Most have four cone types including an ultraviolet channel, sharpened further by coloured oil droplets in front of each cone. Plumage that looks plain to us can carry bright UV patterning.
Twelve: the mantis shrimp is the great exception in the other direction. It has twelve to sixteen photoreceptor types, more than any other known animal, and behavioural experiments show it discriminates similar colours worse than a human does.
Frequently asked questions
- What is the most surprising fact about color blindness?
- That it almost never means seeing in grey. Total colour blindness affects roughly 1 in 30,000 people; everyone else sees a full, saturated world in which particular colour pairs stop being separable from each other.
- Is it true that bulls hate the color red?
- No. Cattle are dichromats and cannot see red as a distinct colour at all. What triggers a charge in a bullring is the movement of the cape — the same cape in any colour, moved the same way, produces the same reaction.
- Can some people see more colors than others?
- Possibly. Women who carry a colour vision deficiency gene have two different versions of a cone pigment and may express four cone types rather than three. Whether that produces measurably better colour discrimination in practice is still debated, and the evidence is far thinner than popular coverage implies.
- Are most animals color blind?
- Most mammals see fewer colours than humans — dogs, cats, horses, cattle, deer and rabbits are all dichromats, close to human red-green deficiency. Birds, many fish and many reptiles go the other way with four cone types including ultraviolet.
Related
Informational only, not medical advice. If you have concerns about your color vision, see an eye-care professional.