How a Colorblind Test Works (and How to Take One)
You've almost certainly seen one: a circle made of colored dots with a number hidden inside. If you can read the number, you probably have typical color vision; if you can't, you might have a color vision deficiency. That's a colorblind test — and the most famous version has a name and a century of history.
The Ishihara test
The classic dotted-circle test is the Ishihara test, created by Japanese ophthalmologist Shinobu Ishihara in 1917. Each image, called a plate, is built from dots in slightly different colors and brightnesses. A number (or winding path) is hidden in one set of dots so that it stands out to people with normal color vision but blends in for people with red-green deficiency — or vice versa.
How it actually works
The trick is that the dots vary in both color and lightness, but randomly. That stops you from spotting the number by brightness alone — you have to use color to see it. If your color vision can't separate, say, red from green well, the figure disappears into the background. Some plates are designed in reverse: the number is only visible to people who are color deficient, which helps confirm a result rather than just hint at one.
What it can and can't tell you
A colorblind test screens for color vision deficiency and can suggest the type and rough severity. But an online test isn't a diagnosis. Screen color calibration, brightness, ambient light, and image compression all change how plates appear, so results on a phone in sunlight aren't reliable. For anything that matters — a job requirement, persistent difficulty with colors — see an eye care professional for a properly calibrated test.
How common is it?
Red-green color blindness is far more common than people expect: it affects roughly 1 in 12 men (about 8%) and around 1 in 200 women. The gap is because the most common forms are linked to genes on the X chromosome. We break down the categories in the types of color blindness.
Test your everyday color perception
A colorblind test asks a specific question: can you separate certain colors at all? A different question — how finely can you tell two very similar shades apart — is just as fun to probe. That's exactly what Spot the Color does: every round, one tile is a hair off from the rest, and it gets closer each time. It's not a medical test, but it's a genuinely good workout for your sense of subtle color difference.