Color Blindness Test
Ishihara-inspired color vision screening with 8 plates — for educational use only.
About this tool
This Color Blindness Test presents eight Ishihara-inspired plates generated entirely in the browser using HTML5 canvas. Each plate shows a pattern of coloured dots in which a number is visible to people with normal colour vision but hidden or altered for those with red-green or blue-yellow colour vision deficiencies. Work through all eight plates, selecting the number you see or choosing 'Can't see it'. After the final plate the tool summarises your responses and suggests a likely colour vision category: Normal, Red-Green Deficiency (protanopia/deuteranopia), Blue-Yellow Deficiency (tritanopia), or Total Colour Blindness. A disclaimer reminds users this is an educational screening tool only and cannot replace a professional ophthalmological examination.
How to use
- 1 Read the on-screen instructions and note the educational disclaimer.
- 2 Look at each plate and select the number you can see in the dot pattern.
- 3 Choose 'Can't see it' if the number is not visible to you.
- 4 Click Next to advance to the following plate.
- 5 After all 8 plates, read your result summary and suggested colour vision type.
- 6 Consult an eye-care professional if you are concerned about your colour vision.
How an Ishihara-style plate hides a number
The dotted circles you see here borrow a 100-year-old idea. A plate is filled with hundreds of coloured dots of varying size and brightness. A figure — usually a number — is drawn in dots of a different hue from the surrounding background, but at a similar lightness. To someone with normal colour vision the hue difference makes the figure pop out instantly. To someone whose eyes confuse those particular hues, the figure blends into the background and either disappears or looks like a different number. The clever part is that brightness alone gives nothing away: because the figure and background dots are roughly equal in lightness, you cannot cheat by spotting a dark shape. Only colour discrimination reveals the answer.
This tool builds eight such plates entirely in your browser with HTML5 canvas. It scatters about 500 random background dots in one hue family, then stamps the target number using a small 5×7 dot font in a confusable hue, jittering each dot's position, size, and shade so the pattern looks organic rather than printed. The whole canvas is finally clipped to a circle.
What each plate is testing
The eight plates are not interchangeable — each is tuned to a specific kind of colour confusion:
| Plate type | Hue pairing | Catches |
|---|---|---|
| Normal (control) | Easily distinguished hues | Almost everyone reads these — they verify the test is working |
| Red–green | Greens vs. reds/oranges | Protanopia and deuteranopia |
| Blue–yellow | Blues vs. yellows | Tritanopia |
Of the eight plates, two act as controls, several target red–green confusion (by far the most common deficiency), and a couple target the rarer blue–yellow type. After the last plate the tool counts your correct answers and weighs which kinds you missed. Miss several red–green plates while reading the blue–yellow ones, and it suggests a possible red–green deficiency; the reverse points toward blue–yellow. Get seven or more right overall and it reports likely normal colour vision.
A worked example of the scoring
Suppose you correctly read both control plates and the blue–yellow plates, but you cannot make out the numbers on three of the red–green plates and guess wrong. Your score is 5 out of 8. Because the misses cluster in the red–green category (three misses there, none in blue–yellow), the result reads "Possible Red-Green Deficiency," noting that this pattern can reflect protanopia or deuteranopia. Had you instead missed only the blue–yellow plates, the same five-correct score would point to a possible blue–yellow deficiency. The number of correct answers and the pattern of the errors together drive the conclusion.
Who is affected, and by what
- Red–green deficiency is the common one, affecting roughly 8% of men and about 0.5% of women of Northern European descent. It is inherited on the X chromosome, which is why it is far more frequent in males. People with it confuse reds, oranges, greens, and browns.
- Blue–yellow deficiency (tritanopia) is rare — on the order of 0.01% of people — affects men and women roughly equally, and is usually not hereditary. It muddles blue with green and yellow with violet.
- Total colour blindness (seeing only in shades of grey) is rarer still and usually comes with other vision problems.
Why this is a screening, not a diagnosis
Read the disclaimer the tool shows and take it seriously: this is for education and curiosity, not medicine. Three things outside the test's control can swing your result. First, screen calibration — every monitor reproduces colour slightly differently, and an uncalibrated or colour-managed display can make a plate easier or harder than intended. Second, ambient light — glare and warm room lighting shift how you perceive hues. Third, the plates are generated with randomised dots rather than clinically validated artwork. A genuine diagnosis requires standardised Ishihara plates administered under controlled lighting by an optometrist or ophthalmologist, often alongside other tests.
Practical tips for a fairer self-check
- View at full brightness in a neutrally lit room, not in direct sunlight and not in a dim one.
- Sit at a normal reading distance and look at the plate as a whole rather than hunting dot by dot.
- Do not overthink it. The number should appear quickly or not at all; long deliberation usually means guessing.
- Choose "Can't see it" honestly. A truthful "no figure visible" is more diagnostic than a lucky guess, because the scoring distinguishes a wrong number from a blank.
- Re-take it if you suspect your screen skewed a plate — the dots are regenerated each run, and a second attempt can rule out a one-off rendering quirk.
Why the plates are generated, not scanned
Real Ishihara plates are copyrighted clinical material and cannot be freely reproduced. This tool instead recreates the same underlying principle — hiding a figure inside a field of confusable hues at matched lightness — procedurally, so it can offer the experience legally and adapt the colours on the fly. If the result concerns you, the right next step is always a professional eye exam.