👁️Colour Blindness Test

About this tool

Each of ten plates shows a circle of coloured dots with a number hidden in it. Type the number you see, or press I see no number. At the end you get a summary and a plate-by-plate table of what each one showed and what you answered. Use full screen brightness, turn off night mode or blue-light filters and view from about arm's length. Take it again for a new set of dot patterns.

How colour vision screening works

Most people have three types of cone cell in the retina, sensitive to long (red), medium (green) and short (blue) wavelengths. In colour vision deficiency, one type is missing or works differently. Red-green deficiencies, protan and deutan, are by far the most common, affecting about 1 in 12 men and 1 in 200 women of Northern European descent, because the genes involved are on the X chromosome. Blue-yellow (tritan) deficiency is rare. The Ishihara test, published in 1917, hides numbers in dot patterns whose colours differ in hue but have similar brightness, so the number stands out only if you can tell those hues apart. These plates follow the same idea: most use orange or pink figures on green-grey backgrounds, which are hard to separate with a red-green deficiency, two use blue against grey-yellow, and two control plates use brightness contrast that anyone should be able to read. If you miss a control plate, the result isn't reliable. Honest limits: these are generated, uncalibrated screen plates, not the printed Ishihara book, and screens, brightness, viewing angle and room lighting change colours a great deal, so this can't diagnose or rule out colour blindness. If you're concerned, or need a result for a job, licence or school, see an optician or optometrist, who can test you properly. The colourblind simulator shows how images look with different deficiencies and the colour hue test checks fine hue discrimination.

Frequently asked questions