How to take the colour blind test
- Check your screen. Turn off Night Shift, Night Light and any blue-light or colour filter, use normal brightness and make sure the ten grey steps in the Quick screen check look neutral.
- Press Start the colour blind test and sit at a normal reading distance with your usual glasses or contact lenses on.
- For each of the 20 dot plates, tap or type the number you see, or press I can't see a number (N). There is no time limit; Previous plate fixes a slip.
- In the Hue arrangement test, build a row from the reference cap R, always adding the cap most similar to the last one, then press Done, show my results (or Skip this part).
- Read the Results: an overall screening result, a plate-by-plate table and a diagram of your arrangement.
How dot plates work
A dot plate, or pseudo-isochromatic plate, is a circle of dots of different sizes and brightness. Some dots form a number; the rest are background. Their colours differ in hue but not in a way brightness can reveal, so typical colour vision sees the number at once, while someone who cannot tell those two colours apart sees only random dots.
Our plates are generated fresh every time by our own algorithm, not copied from any printed test. Each colour is converted into the responses of the three cone types in the eye: long-wavelength (L, "red"), medium-wavelength (M, "green") and short-wavelength (S, "blue"). On a protan plate the number and background differ only for the L cones, on a deutan plate only for the M cones and on a tritan plate only for the S cones. Such pairs lie on a confusion line: they look identical to someone missing that cone type. Every dot also gets a random brightness, so the number cannot be found by lightness.
Control plates use a brightness difference almost everyone can read and check that the screen and instructions work. Vanishing plates, in strong and subtle versions, can disappear with a colour vision deficiency. Two-number plates show, for example, 8 to typical colour vision and 3 to someone who cannot see part of the figure.
How the hue arrangement test works
The second part follows the idea of panel tests such as the D-15, with our own 15 caps plus a reference. The caps share the same lightness and colour strength and step round a colour circle from blue through green, yellow and red to purple. Typical colour vision follows the circle. With a colour vision deficiency, caps from opposite sides look alike, so the row jumps across it. The diagram joins your caps in order: a neat ring is typical, while several parallel lines across the circle point to a protan, deutan or tritan confusion axis (the dashed lines).
Types of colour vision deficiency
| Type | Cone affected | What it means |
|---|---|---|
| Protanopia / protanomaly | L (red) | Red cones missing or shifted. Reds look darker and can be confused with greens, browns and greys. |
| Deuteranopia / deuteranomaly | M (green) | Green cones missing or shifted. Greens, yellows, oranges and reds are easily confused. Deuteranomaly is the most common form. |
| Tritanopia / tritanomaly | S (blue) | Blue cones missing or weak. Blue and green, and yellow and pink or grey, are confused. Rare when inherited. |
| Achromatopsia | Cone function very limited | Little or no colour vision, usually with light sensitivity and reduced sharpness. Very rare. |
The endings matter: -opia means one cone type is missing, so the person is a dichromat; -anomaly means all three cone types are present but one is shifted, which is milder and varies a lot from person to person. Protan and deutan types together are called red-green colour vision deficiency, and on many tests they are hard to separate, which is why the result here says "protan/deutan type".
How common is colour blindness?
Red-green colour vision deficiency is by far the most common type and is much more common in men than in women. A commonly cited estimate is roughly 1 in 12 men and 1 in 200 women of Northern European ancestry, with lower figures reported in many other populations. Inherited blue-yellow deficiency and complete colour blindness are rare.
Inherited and acquired colour vision deficiency
Most red-green deficiency is inherited through the X chromosome: men have one X, so one changed gene is enough, while women usually need it on both. Inherited deficiency is present from birth, affects both eyes equally and does not get worse.
Colour vision can also change later in life. Cataracts, glaucoma, macular and optic nerve conditions, diabetic eye disease and some medicines can alter colour perception, often in one eye more than the other. If your colour vision seems to have changed, see an optometrist or doctor rather than relying on an online test.
Living with colour vision deficiency
- Tell teachers and colleagues, and ask for labels, patterns or text instead of colour alone on charts, maps and cables.
- Try the colour filters built into phones and computers, or a camera app that names the colour you point at.
- Some jobs, such as pilot, electrician or train driver, have colour vision standards; check them early and get a formal test.
- If you design slides, charts or websites, make them colour-blind friendly: avoid red against green, add labels and keep strong lightness contrast.
Check other parts of your vision with the online eye test, the astigmatism test and the Amsler grid test, or try the online hearing test. More screenings are on the health tests page. None of them replaces a regular eye examination.
Privacy: the plates are drawn in your browser and your answers never leave your device. Only the last result is saved, in this browser's local storage, and Clear deletes it.
Frequently asked questions
Is an online colour blind test accurate?
It is a useful first check, not a diagnosis. Screens show colours differently, and filters and lighting change them. If several plates point the same way, book a colour vision test with an optometrist, who uses calibrated plates under standard light.
Can women be colour blind?
Yes. Inherited red-green deficiency is much less common in women because they usually need the changed gene on both X chromosomes, but it happens. Many women are carriers, and anyone can develop acquired colour vision changes.
Can colour blindness be cured?
Inherited colour vision deficiency cannot currently be cured, though it does not get worse. Gene therapy has been studied in research but is not an available treatment. Acquired changes are different: treating the cause, such as cataract surgery, can sometimes improve colour vision.
What is the most common type of colour blindness?
Deuteranomaly, a milder red-green type in which the green-sensitive cones are shifted, is the most common form. Together with the other protan and deutan types it makes up the large majority of colour vision deficiency.
Do colour blind glasses fix colour blindness?
No glasses restore normal colour vision. Tinted colour-enhancing glasses filter some wavelengths, which can make certain colours look more distinct for some people with red-green deficiency. They do not replace missing cone responses, results vary from person to person, and they should not be worn during a colour vision test.
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