Color Blindness Simulator

See how your colors and images look to people with each of the seven common types of color vision deficiency. Pick a color or upload an image, and every simulation renders side by side.

By iwantfreecolortools.com Team

Related Guide: Accessible Color Design: A Practical Guide

Quick Answer

Color blindness, properly called color vision deficiency, comes in seven common forms. Protanopia, deuteranopia and tritanopia mean the red, green or blue cone is missing entirely. Protanomaly, deuteranomaly and tritanomaly mean that cone works but is shifted, giving a milder version. Achromatopsia means no color cones function at all, leaving only shades of grey. Red and green confusion is by far the most common, affecting around 1 in 12 men.

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Drop an image here or click to choose
PNG, JPG, WebP or GIF. A chart, a UI screenshot or a logo works well.
Nothing leaves your device. The simulation runs on a canvas inside this page. No image, color, or result is uploaded or sent anywhere, and there is no server involved in the processing at all.

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How the simulation works

Each simulation applies a 3 by 3 color transformation matrix taken from Machado, Oliveira and Fernandes (2009), a physiologically based model published in IEEE Transactions on Visualization and Computer Graphics. The model derives its matrices from how cone cells actually respond to light, and it parameterises severity, which is what allows the same framework to produce both the complete forms such as deuteranopia and the partial forms such as deuteranomaly.

One detail matters for accuracy and is often skipped. The matrices operate on linear light, not on the gamma encoded values stored in an image file. This tool converts each pixel from sRGB to linear RGB, applies the matrix, then converts back. Skipping that step produces simulations that look roughly right but shift the lightness of every color, which is exactly the property you are usually trying to judge.

Achromatopsia is handled separately, as a luminance conversion using the Rec. 709 coefficients, since it is the absence of all cone based color rather than a shift between cone types.

Frequently Asked Questions

Color blindness, more accurately called color vision deficiency, is a reduced ability to distinguish certain colors. It is rarely an absence of color. Normal vision uses three types of cone cell in the retina, each most sensitive to long, medium or short wavelengths. When one type is missing or shifted in its sensitivity, colors that depend on comparing those cones become hard to tell apart. Red and green confusion is by far the most common form, and complete absence of color is very rare.
Roughly 1 in 12 men and 1 in 200 women of Northern European descent have some form of color vision deficiency, which is about 8 percent and 0.5 percent respectively. The imbalance exists because the genes for the long and medium wavelength cones sit on the X chromosome, so a single altered copy affects men while women usually have a second copy to compensate. Deuteranomaly alone accounts for around 6 percent of men, making it the single most common form.
The name tells you which cone is affected and how severely. Prot refers to the long wavelength red cone, deuter to the medium wavelength green cone, and trit to the short wavelength blue cone. The ending anopia means that cone type is absent entirely, while anomaly means it is present but shifted in sensitivity, producing a milder effect. So deuteranopia is the absence of the green cone and deuteranomaly is a weakened version of it. Achromatopsia is the rare condition of having no working color cones at all.
Because any information carried by color alone disappears for a significant share of your audience. Red and green status indicators, a chart whose series are distinguished only by hue, a required form field marked only in red, or a link that differs from body text only in color all fail. WCAG Success Criterion 1.4.1 addresses exactly this and requires that color is never the only visual means of conveying information. The fix is usually to add a second channel such as a label, an icon, a pattern, or a difference in lightness.
It is a good approximation and not a medical assessment. The simulation applies published color transformation matrices derived from a physiological model of cone response, which is the same approach used by most professional accessibility tooling. Real color vision varies considerably between individuals with the same diagnosis, severity is a spectrum rather than a fixed value, and the brain adapts in ways a matrix cannot capture. Use it to catch designs that clearly fail, not to conclude that a marginal design definitely passes.
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Source: Transformation matrices from Machado, G. M., Oliveira, M. M., and Fernandes, L. A. F. (2009), A Physiologically-based Model for Simulation of Color Vision Deficiency, IEEE Transactions on Visualization and Computer Graphics 15(6). Prevalence figures from Colour Blind Awareness. Design requirements from WCAG 2.2 Success Criterion 1.4.1 Use of Color.