Achromatopsia Simulator

Achromatopsia Simulator reduces a color to the neutral tone a viewer with no color vision would see, which is the most demanding test a palette can face.

What is Achromatopsia Simulator?

Achromatopsia Simulator shows a color and the neutral tone it becomes when no color signal is available at all. The comparison is stark by construction, because the simulated side is always a grey: the original and the result differ only in lightness, and every distinction the design was making with hue is gone.

Achromatopsia is the complete absence of color vision, and it is rare, but the simulation is still the most useful stress test in the set:

• The simulated swatch is guaranteed neutral, since the same luminance weight is applied to all three output channels.
• Only lightness survives, so any two colors that were separated by hue alone will collapse together.
• It is a stricter test than any of the single-channel deficiencies, because none of the three color axes is available.
• Designs that pass it are almost always safe for the other deficiencies, since they have been forced to encode information in lightness rather than hue.

The conversion uses a single luminance formula applied identically to each output channel: 0.299 of the red value, 0.587 of the green and 0.114 of the blue. Those are the recursive luminance weights that standard grayscale conversion uses, and because the same total is written to red, green and blue, the result is neutral by definition. The arithmetic happens on the 8-bit channel values and is clamped into the 0 to 255 range before being written out as hex. Note how much of the total comes from green: a green color converts to a much lighter grey than a blue of the same apparent brightness, which is why two colors that look equally vivid can land at very different greys.

The page is deliberately minimal, and that is its limitation as much as its strength.

• One color at a time, so a palette has to be worked through entry by entry.
• No image simulation on this page.
• The output is a single grey per color, with no intermediate or partial color vision option.
• It does not tell you whether the resulting greys are distinguishable from each other, which is the question that actually decides whether a palette survives.
• The grey is a model of how the colors convert, not a claim about any particular viewer's perception.

Use it as the final check on a chart or a status system, after the individual pairs have passed their contrast thresholds. The practical test is to collect the grey values of every color in a set and ask whether they are far enough apart to be told apart at a glance, because that is the only channel left. Where two greys are close, increase the difference in the original colors' lightness rather than changing their hues.

As a total color blindness simulation the page is the bluntest check available, which is precisely why it is worth running first on a chart. The luminance conversion it applies uses the standard grayscale weights, so the result is also what you would see if the artwork were printed in black and white. That makes it dual-purpose: a palette that survives this check is both more robust for viewers and safer for grayscale reproduction.

How to use Achromatopsia Simulator

1. Enter a color in the swatch field to see it beside its grayscale conversion.
2. Note the hex value of the simulated swatch, which is always a neutral tone.
3. Repeat for each color in the palette, and compare the resulting greys against each other rather than one at a time.
4. Where two greys are close, adjust the lightness of the original colors until the neutral versions separate.

When to use Achromatopsia Simulator vs related tools

Use the achromatopsia simulator as the strictest check on a palette, especially for charts, status colors and anything that has to work in print or in a grayscale reproduction. It pairs well with the color blindness simulator when you want all four deficiencies in one row, with the palette accessibility checker when the question is contrast rather than separation, and with the text readability checker when the neutral result needs to be judged as actual text on a surface.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

Frequently asked questions about Achromatopsia Simulator