That’s not Red
01 What colorblindness actually looks like
One photo, both waysDeuteranomaly · 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 What they seeSimulated

The thing everyone gets wrongThe most common misconception

Everyone assumes grey. Almost nobody sees grey. What's common is 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.

Why this happens, and who it happens toPhysiology, prevalence and inheritance

What people assume
A canopy of umbrellas strung over a street, shown with all color removed.
What it actually is
The same umbrellas in full color vision loss: still colorful, but the pink and orange ones nearly match.

The left is the myth. The right is the real thing: plenty of color, just fewer differences. The pink and orange canopies are on their way to being one.Left: luminance-only rendering, the popular misconception. Right: Machado deuteranomaly at 0.80. Chromatic content is preserved; discrimination between specific hue pairs is not.

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
A stack of folded linen: olive green, cream, blush, terracotta red, dusty rose, sage, and mustard, in bands one on top of another.
03With red-green colorblindness
The same stack, with the terracotta and the olive now the same dull khaki, so several of the bands run together.

Six colours going in. Four coming out.Adjacent bands converge pairwise under the red-green transform.

What shiftsConfusion axisRed and olive into one khakiRed, olive → common khaki
How much of the frame changesConvergent area36% of it
What's left to go onRemaining cueThe order they are stacked inLuminance ordering, edge position

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.