Am I Colourblind? Types, Causes and How to Check
About 1 in 12 men and 1 in 200 women have colour vision deficiency. Learn the types, why it runs in families, how to do a quick online check, and when to see an eye doctor.
You have probably sailed through life never questioning your colour vision — until someone points at a map legend, asks you to find the ripe tomato, or shows you one of those dotted Ishihara circles and gives you an odd look. The question "am I actually colourblind?" is more common than most people expect.
Try the check first
The plates below work the same way as the Ishihara test used in clinics: dots of similar brightness but slightly different hue are arranged so that people with typical colour vision see a number, while those with red-green deficiency see nothing — or a different number. It takes about two minutes.
Key takeaways
- Red-green CVD affects ~8% of men and ~0.5% of women — around 300 million people worldwide.
- The most common form is deuteranomaly: a reduced sensitivity to green wavelengths.
- Red-green CVD is X-linked, which is why men are affected far more often than women.
- Online tests are a screen, not a diagnosis — monitor calibration and lighting both affect the result.
What colour vision deficiency actually is
Your retina contains roughly 6 million cone cells concentrated in a central region called the fovea. They come in three types, each tuned to a different band of the visible spectrum: long wavelength (L, perceived as red), medium wavelength (M, green), and short wavelength (S, blue). Precise colour perception depends on comparing the signals from all three types simultaneously.
CVD occurs when one or more cone type is absent, has reduced sensitivity, or has a shifted spectral tuning. The result is a smaller palette — colours that should appear distinct can collapse into the same apparent shade.
8%
of men worldwide have colour vision deficiency
National Eye Institute — the vast majority have red-green CVD
The main types
Red-green CVD is by far the most common category. Blue-yellow CVD (tritanopia/tritanomaly) is rare, and total colour blindness (achromatopsia) is very rare.
| Type | Cone affected | What's harder to see | Prevalence in men |
|---|---|---|---|
| Deuteranomaly | M cones (reduced) | Red vs green; some greens appear brownish or muddy | ~5% |
| Deuteranopia | M cones (absent) | Reds, greens, and some oranges all appear similar | ~1% |
| Protanomaly | L cones (reduced) | Red appears darker; red–green confusion | ~1% |
| Protanopia | L cones (absent) | Reds appear black or dark grey; strong red–green confusion | ~1% |
| Tritanomaly / Tritanopia | S cones (reduced or absent) | Blue vs green, yellow vs violet | Under 0.01% |
| Achromatopsia | All cones (absent) | No colour at all; only light and dark | Very rare |
Deuteranomaly is the most common single type, accounting for roughly five out of every hundred men. Most people who wonder "am I colourblind?" have deuteranomaly — their green sensitivity is shifted, so certain greens, reds, and browns blur together. They may have adapted so well that they never noticed until a test caught it.
Why it runs in families — especially through the male line
The genes for L and M cone opsins sit on the X chromosome. Men carry only one X chromosome (alongside a Y), so a single defective copy is enough to cause CVD. Women carry two X chromosomes; if one copy of the gene is faulty, the other can compensate. That is why red-green CVD is far more common in men.
Blue-yellow CVD (tritan defects) follows a different path: it is autosomal dominant, caused by mutations on chromosome 7, and affects men and women in roughly equal numbers.
Myth
Colourblind people see only black and white.
Everyday impact and practical workarounds
Most people with CVD live full, unrestricted lives. But certain situations genuinely trip you up.
Common friction points — and how to handle them
- Traffic lights — The red–green pair can look identical at distance, particularly in bright sun. Position is your friend: the top light is always red, bottom is always green. Most modern lights also differ slightly in brightness.
- Food and ripeness — A banana that looks yellow to you may still look green to others, and a rare steak can look the same as a well-done one. Good workarounds: use a meat thermometer, rely on texture cues, and ask.
- Colour-coded maps, charts, and infographics — This is one of the most consistent frustrations. Asking for a high-contrast or labelled version is entirely reasonable, and most design tools now offer CVD-safe palettes.
- Careers with colour requirements — Certain roles — electrical wiring, some aviation and maritime jobs, some branches of the military — have formal colour-vision standards. It is worth checking early; many workarounds exist, and many jobs have no restriction at all.
Colour vision deficiency is the world's most common inherited visual condition — yet most people are diagnosed by accident, often in childhood.
What your result means
If you missed plates in a particular pattern — for example, consistently seeing numbers in the green family but missing red-family numbers — that points toward a specific deficiency type. A single missed plate on a screen isn't a diagnosis; it could reflect monitor settings, ambient light, or simply a moment of inattention. What matters is the overall pattern across several plates.
Online tests versus clinical testing
The Ishihara check on your screen is a good starting point, but it has real limitations. The original Ishihara plates were designed for use under controlled lighting (Illuminant C or D65) with precisely printed pigments. A consumer monitor — even a good one — reproduces colour differently depending on its panel type, calibration age, brightness setting, and ambient light. The red-green confusion can look subtly different on two different screens, which means a borderline case might pass on one device and fail on another.
When should you book an eye test?
- You consistently miss plates or see different numbers from others in the room.
- A family member has CVD (one parent can affect all sons on the maternal side).
- Your child seems confused about colours well past the age when they should be confident naming them.
- Your colour vision seems to have changed recently — acquired CVD can be a sign of retinal or optic-nerve disease and needs prompt review.
Frequently asked questions
How common is colour blindness?
Is colour blindness the same as not seeing any colour?
Can colour blindness be cured or corrected?
Will my children be colour blind if I am?
Is a free online colour blindness test accurate enough?
Free interactive test · ~3 min
Check your colour vision now — it takes two minutes
Ishihara-style plates, instant feedback on which colour pairs you might be confusing, and a result you can save and share with your optometrist.
Take the colour vision testKeep reading
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References
- 1.National Eye Institute (NEI). Color Blindness. NIH.
- 2.Neitz J, Neitz M. (2011). The genetics of normal and defective color vision. Vision Research. PMC.
- 3.Colour Blind Awareness. About Colour Blindness.
- 4.American Academy of Ophthalmology. How Color Blindness Is Tested.
- 5.Colour Blind Awareness. Living with Colour Vision Deficiency.
This guide is educational and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified clinician about your individual circumstances.