How to take the color blindness test
- Turn off anything that tints your screen — night mode, Night Shift, True Tone, blue-light filters, color filters — and set the brightness high. Sit at about arm’s length and look at the screen straight on.
- Press Start the test. Each plate is a circle of dots of different sizes and shades; some of them form a number from 0 to 9.
- Tap the number you see, type it on your keyboard, or tap I see no number. Don’t study a plate for long: professional tests allow about three seconds per plate.
- After 15 plates you see your score for each group of plates, a plain-language screening result and, under Your answers, which plates you read differently.
Every test is new: the dot pattern, the number on each plate and the order of the plates are chosen at random, so you can retake it without remembering answers.
How the plates work
Normal color vision uses three kinds of cones in the retina, sensitive to long (L, “red”), medium (M, “green”) and short (S, “blue”) wavelengths. A person who lacks one kind — a dichromat — can’t tell apart two colors that differ only in what that missing cone would see. All such color pairs lie on confusion lines, which in the CIE 1931 color chart all pass through one point per type: about x = 0.747, y = 0.253 for protan, x = 1.40, y = −0.40 for deutan and x = 0.171, y = 0.000 for tritan.
This test computes its plate colors from the cone model of Viénot, Brettel & Mollon (1999), which converts screen colors (sRGB) into L, M and S cone signals. For a protan plate, the number and the background are placed on either side of one color, shifted only along the direction that changes the L-cone signal; deutan plates shift only the M signal, tritan plates only the S signal. Every dot also gets its own random brightness (±20%), so the number can’t be found by lightness alone — just as on printed plates. The separation shrinks from plate to plate: the first plates of each type catch strong deficiencies, the subtler ones the milder (anomalous) forms.
Example: the strongest protan plate
Its two colors are #dd905b and #37a35d (each dot brighter or darker). For normal vision their difference is ΔE 71.9 — the CIE76 color difference, where about 2.3 is the smallest difference people notice. Run through the protanopia simulation of Machado, Oliveira & Fernandes (2009), the same two colors differ by only ΔE 1.7: below what anyone can see, so a protanope sees no number. The deuteranopia simulation still shows a difference of ΔE 20.7, which is why the protan and deutan plates can point to different types.
How to read your result
| Your answers | What the test reports |
|---|---|
| All plates right | No sign of a color vision deficiency |
| 1–2 color plates missed | Probably normal — retake the test |
| 3 or more of the 10 red-green plates missed | Possible red-green deficiency; protan or deutan when one line has at least 2 more misses than the other |
| 2 or 3 of the 3 blue-yellow plates missed | Possible blue-yellow (tritan) deficiency |
| A control plate missed | Result not reliable — check the screen and retake |
The two control plates differ in lightness, not just color, so people with any type of color vision deficiency read them. Missing one means the screen, the lighting or a slip got in the way.
Types of color vision deficiency
| Type | Cones affected | What it does (National Eye Institute) |
|---|---|---|
| Deuteranomaly | M cones shifted | Certain greens look redder; mild, the most common type |
| Protanomaly | L cones shifted | Certain reds look greener and less bright |
| Protanopia, deuteranopia | L or M cones missing | Red and green can’t be told apart at all |
| Tritanomaly, tritanopia | S cones shifted or missing | Blue vs green and yellow vs red (or pink) are confused |
| Achromatopsia (monochromacy) | Cone function missing | No color at all; also light sensitivity and low sharpness |
Source: NEI, Types of Color Vision Deficiency.
How common is color blindness?
Red-green deficiency is by far the most common type. Among people of Northern European ancestry it affects about 1 in 12 men and 1 in 200 women (MedlinePlus Genetics); a review of large surveys puts it at about 8% of men and 0.4% of women of European descent and 4–6.5% of Chinese and Japanese men (Birch, J Opt Soc Am A 2012). Men are affected far more often because the genes for the L and M cone pigments (OPN1LW, OPN1MW) sit on the X chromosome. Blue-yellow defects come from the OPN1SW gene on chromosome 7, affect men and women equally and occur in fewer than 1 in 10,000 people. Achromatopsia affects about 1 in 30,000 people.
Color vision can also change later in life: eye diseases, some medicines, injuries and aging can all affect it (NEI). A change you notice in adulthood, especially in one eye, is a reason to see an eye doctor soon.
How professionals test color vision
- Ishihara plates — the best-known dot-number test, printed for viewing in daylight. It screens for red-green defects only.
- HRR plates (Hardy-Rand-Rittler) — use shapes instead of numbers, cover red-green and blue-yellow defects and grade them as mild, medium or strong.
- Arrangement tests such as the Farnsworth D-15, where colored caps are put in order; the pattern of errors shows the type.
- Anomaloscope — the reference instrument for diagnosing the type and severity of red-green defects, used when a job or license requires it.
Young children who don’t know numbers yet are tested with shape or symbol plates by an eye-care professional.
Why an online test has limits
Printed plates have known colors under known light. A screen does not: its color calibration, brightness and white point vary, and night modes, True Tone and blue-light filters deliberately shift colors toward yellow — which can make blue-yellow plates hard for anyone. The cone model describes an average observer, and the plates can’t measure severity the way an anomaloscope does. Treat a result here as a reason to get checked, not as an answer. If you have a deficiency, the color picker can name the color of anything in a photo.
Important: this test is a screening for general information and is not medical advice. It cannot replace an examination by an optometrist or ophthalmologist.
Frequently asked questions
Is this the Ishihara test?
No. The Ishihara plates are a printed, copyrighted test used by eye-care professionals. This page draws its own plates on the same principle — numbers hidden in dots whose colors lie on confusion lines — computed from a published model of the eye’s cones.
Can an online test diagnose color blindness?
No. It can only screen. Screens show colors differently, and filters such as Night Shift or blue-light modes change them. An optometrist or ophthalmologist diagnoses color vision deficiency with standardized plates under controlled light or with an anomaloscope.
Can kids take the color blindness test?
Children who know the digits 0 to 9 can take it with an adult who reads the instructions. Younger children and toddlers are tested by eye-care professionals with symbol or shape plates instead of numbers.
I missed only the blue-yellow plates. Am I tritan?
Probably not. Inherited blue-yellow defects are rare (fewer than 1 in 10,000 people), while warm screen tints from night modes and blue-light filters are common and make exactly these plates hard. Turn the filters off and retake the test; if the result stays the same, see an eye doctor — acquired blue-yellow changes can come from eye disease.
Is there a cure for color blindness?
There is no cure for inherited color vision deficiency, but most people adapt well. Special tinted glasses or contact lenses can increase the contrast between some colors for some people without restoring normal color vision, and phone apps can name colors. When the cause is a disease or a medicine, treating the cause can help.
Why do men have color blindness more often than women?
The genes for the red- and green-sensitive cone pigments are on the X chromosome. Men have one X, so one altered copy causes the deficiency; women have two and are usually carriers without being affected.
Last updated: October 15, 2026