01 What colorblindness actually looks like
Deuteranomaly · 0.80 · Machado 2009

Colorblind is not one thingDeficiency types are distinct conditions

Colorblind doesn't mean black and white.Color vision deficiency is not achromatopsia.

It means certain colors argue with each other until your brain stops trying to tell them apart. And a few colors just read wrong on their own, with nothing to compare them to. Here's what that actually looks like.Overlapping cone response curves compress specific regions of the spectrum. Color perception persists in full; discrimination between particular hues does not. Isolated colors can also be misidentified outright, with no comparison available to correct the error.

Find out what you seeTake the screening test Or just look aroundSkip to the simulator

Normal visionUnmodified A boy seen from behind in a red jersey numbered six, standing alone on a green artificial turf field with a goal in the distance.
What they seeSimulated The same photo, the red shirt now sitting close enough to the green field that it barely stands out.

The thing everyone gets wrongThe most common misconception

Almost everyone assumes colorblind people see the world in grey. Almost nobody does. That's a different condition, and it's rare enough that you've probably never met someone who has it. What's common is much stranger: you see colors fine, you just can't always tell two of them apart. A red shirt and a green shirt can be the same shirt. Not similar. The same.Complete achromatopsia (the total absence of color perception) affects roughly 1 in 30,000 people. Anomalous trichromacy is around 8% of men. In anomalous trichromacy all three cone types function, but one responds to a shifted range of wavelengths, collapsing the perceptual distance between hues that a typical observer separates easily. The result is not desaturation. It is confusion between specific pairs.

The top row is the colour. The bottom row is what arrives. Count them: the bottom row has two fewer colours than the top one. Olive and brown are the same swatch now, and so are navy and purple.Upper row: source values. Lower row: the same values under deuteranomaly at severity 0.80. Two pairs, olive/brown and navy/purple, fall below the discrimination threshold and render as single fields.

02 Pictures that stop working
02 · 03
02Normal vision
Ripe red berries scattered through dense green leaves.
03Deuteranomaly · 0.80 · Machado 2009
The same branch, with the berries now a dull yellow-brown, the colour of the dead leaves behind them. They are still perfectly easy to see. They just no longer look like fruit.

The berries do not disappear. Look again: they are right there, and they are the colour of dead leaves. Nothing is missing, so nothing looks wrong. That is the part that is hard to explain, and it is why ripe and rotten is a guess.Frugivory is the standard evolutionary account of primate trichromacy. Under a red-green transform the berries retain their full luminance contrast against the foliage and remain trivially detectable; what is lost is the chromatic signal that classifies them as ripe. The failure mode is misidentification, not omission.

What shiftsConfusion axisRed into yellow-brownRed → yellow-brown
How much of the frame changesConvergent area88% of it
What's left to go onRemaining cueBrightness and shapeLuminance contrast, outline

Stop explaining it. Send the link instead.Share a configured simulation

Take the test, get a link that's yours, send it to whoever keeps asking. They'll see the same photos you do, filtered the way you actually see them, with the explaining already done.The screening result generates a shareable URL that opens the simulator pre-configured to your deficiency type, alongside a plain-language description of what that type affects.

Find out what you seeTake the screening test See what a shared link looks likeView an example shared profile

The seam above is two colours. For most colorblind viewers it is one.The diagonal above is a crimson/pine boundary. Both fields converge under a red-green transform.