Color Blindness Simulator

This simulates how colours may appear. It is not a WCAG audit and it does not produce a pass or fail - for a measured contrast ratio use the Contrast Checker

Palette

Normal vision

Protanopia (no red cones)

Deuteranopia (no green cones)

Tritanopia (no blue cones)

Achromatopsia (no colour)

Image

The image is read from your device and simulated in a canvas in the tab. It is never uploaded to FindUtils. The page itself loads advertising and analytics scripts like the rest of the site.

How to check a palette for colour vision deficiency

Enter your colours

Edit the swatches to your real palette. Chart series, status colours and category colours are the ones worth checking first.
Read the four strips

Each strip shows the same palette under one deficiency. Two swatches that become the same colour are the problem to fix.
Try a real screenshot

Choose an image of the actual interface. A palette can survive in isolation and still fail once it is on a page with text over it.
Fix with more than hue

Separate the affected pairs by lightness, or add a shape, a label, a pattern or an icon so the meaning does not depend on colour alone.

Common Use Cases

Chart and graph series

Red and green series are the classic failure. Checking the strip shows immediately whether two lines merge.

Status and validation colours

Success green and error red are the most common meaning-by-colour pair in any interface, and the pair deuteranopia flattens hardest.

Maps and heat scales

A red-to-green scale loses its middle entirely. A sequential single-hue or a blue-to-orange scale survives.

Brand palettes

Check a new brand palette before it reaches production, while changing a colour is still cheap.

Why simulate colour vision deficiency?

Roughly one in twelve men and one in two hundred women has some form of colour vision deficiency, and the most common kinds compress red and green towards the same yellow-brown. A chart whose series are red and green, a form that marks errors only by turning a border red, a status badge that relies on green meaning fine - each of these can be unreadable to a reader you never hear from. Seeing the palette rendered the way those readers see it takes seconds and is far more direct than reasoning about it in the abstract.

Colour vision deficiency is usually a missing or shifted cone response rather than an absence of colour. In protanopia the long-wavelength (red) cones are absent, in deuteranopia the medium-wavelength (green) cones are, and both pull reds and greens towards a similar yellow-brown. Tritanopia, far rarer, affects the short-wavelength cones and confuses blue with green. Achromatopsia removes hue entirely.

This page applies a widely used matrix approximation for each of those to your palette and, if you choose one, to a real screenshot. Two swatches that stay distinct in every strip are safe to use as the only difference between two things. Two that converge are a pair that needs a second signal: a label, an icon, a pattern, or a difference in lightness.

It is important to be clear about what this is not. It simulates appearance; it does not measure anything and it cannot tell you whether a combination passes an accessibility standard. Contrast is a measured ratio, and the Contrast Checker is the tool that reports it against WCAG AA and AAA. Use this page to catch confusable hues and that one to prove legibility. Everything runs in your browser.

How it compares

Browser extensions can simulate deficiency across a whole live page, which is excellent for auditing something already built. This page is for the stage before that: a palette you are still choosing, where you want to see five swatches under four deficiencies at once rather than reload a site four times.

It makes no accessibility claim. Tools that report a pass or fail are measuring contrast ratios, which is a different question from whether two hues are confusable, and both checks are worth doing.

Colour Vision Tips

Deuteranopia and protanopia are by far the most common. If you only check one strip, check deuteranopia.
Never let colour be the only carrier of meaning. Add a label, an icon, a pattern or a position so the information survives without it.
Separating two colours by lightness rather than hue is the single most reliable fix, and it helps in greyscale printing too.
The achromatopsia strip is a good proxy for a black and white printout, even though true achromatopsia is rare.
These are approximations of how the common deficiencies render colour, not a medical model, and individual vision varies.

Frequently Asked Questions

Does this tell me if my palette is accessible?

No, and it deliberately does not claim to. It shows how colours may appear under four deficiencies. Accessibility standards are about measured contrast ratios, which the Contrast Checker reports. A palette can be perfectly distinguishable here and still fail contrast.

Which deficiency should I check first?

Deuteranopia. It is the most common form and it flattens the red-green distinction that most interfaces lean on for success and error states.

How accurate is the simulation?

It uses the standard matrix approximations for each dichromacy, which are good enough to reveal confusable pairs. They are not a medical model, they do not cover anomalous trichromacy where a cone is shifted rather than absent, and individual vision varies.

Is my image uploaded?

No. The file is read from your device and processed in a canvas inside the tab. No request carries the image. Third-party analytics and ads load on the page, as on the rest of the site.

What do I do about two colours that look the same?

Give the distinction a second carrier. Change one colour's lightness rather than its hue, or add an icon, a label, a dash pattern or a position difference so the meaning does not rest on colour alone.

Why does the achromatopsia strip look like greyscale?

Because it is a luminance conversion, which is what a complete absence of colour perception approximates. It doubles as a preview of how the palette will print in black and white.

Can it simulate partial deficiency?

Not yet. It models the dichromacies, where a cone type is missing. Anomalous trichromacy, which is more common and milder, sits between normal vision and these strips.

How to check a palette for colour vision deficiency

Enter your colours

Read the four strips

Try a real screenshot

Fix with more than hue