Tool · Color blind test

Color blind test.

Twelve pseudo-isochromatic plates, freshly generated each time so you cannot memorize them. Read the number in each plate; at the end you get a result for red-green and blue-yellow vision and can view every plate the way each deficiency sees it.

This test is a screening aid, not a medical diagnosis. The plates are generated in your browser from colors that lie on the protan, deutan and tritan confusion lines, but your monitor, brightness, ambient light and any blue-light filter all change how they appear. If the result surprises you, retake it in daylight with filters off, and see an optometrist for a calibrated test.

What is the color blind test?

A color blind test screens for color vision deficiency by asking you to read numbers hidden in plates of colored dots, in the style of the Ishihara test. This online version generates 12 fresh plates each time: one control plate, eight that screen for red-green deficiency (protan and deutan) and three that screen for blue-yellow deficiency (tritan). It takes about two minutes and is a screening aid, not a diagnosis.

How the plates hide a number

Every plate is a disc of dots in several sizes. The dots that form the digit and the dots around it share the same range of lightness, so the number cannot be read from brightness alone. They differ only in hue, and the hue pairs are chosen along the confusion lines of each deficiency: orange against olive-green for red-green plates, blue-violet against green-cyan for blue-yellow plates. For typical vision the two groups are far apart; after the standard protan, deutan or tritan simulation the two groups collapse to nearly the same color and the digit disappears.

Because the plates are generated from a random seed in your browser, they are different on every attempt and cannot be memorized. After the test you can view each plate through the deuteranopia, protanopia and tritanopia simulations, which shows exactly why a plate was hard to read.

What the result means

Reading every plate means this screening found no sign of a deficiency. Missing three or more red-green plates while reading the control plate is the pattern of red-green color vision deficiency, which affects about 1 in 12 men and 1 in 200 women. Missing only blue-yellow plates is rare and is more often caused by a warm-shifted display or a blue-light filter than by tritan deficiency.

Screen calibration, brightness, ambient light, viewing distance and guessing all change the outcome, which is why no online test can diagnose. If the result surprises you, retake it in daylight with any color filter turned off, and see an optometrist for a calibrated Ishihara or anomaloscope test.

How to use the color blind test

  1. Turn off Night Shift, f.lux or any blue-light filter and set brightness to a comfortable level.
  2. Sit at a normal reading distance and read the number in each plate within a few seconds.
  3. Tap the number you see, or "I do not see a number" if the plate looks uniform.
  4. Read the result for red-green and blue-yellow vision, then view the plates through each simulation.

Color Blind Test FAQ

Is this an official Ishihara test?

No. The Ishihara test is a set of printed plates used by eye care professionals under controlled lighting. This tool generates plates on the same principle (pseudo-isochromatic dots along confusion lines) as a screening aid only.

How accurate is an online color blind test?

Good enough to flag a likely red-green deficiency, not good enough to diagnose or grade it. Displays vary, and mild anomalous trichromats may read plates that a calibrated test would catch. Confirm any result with an optometrist.

What is the most common type of color blindness?

Deuteranomaly, a reduced sensitivity to green, is by far the most common form. Together the red-green types affect around 8 percent of men and 0.5 percent of women. Blue-yellow (tritan) deficiency and total color blindness are rare.

Can I test children with this?

Only if they can read digits confidently. For younger children, professional tests use shapes and tracing rather than numbers.

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