How to use the Color Blindness Simulator
- 1. Add colours or an imageType hex colours, upload a screenshot or chart, or both.
- 2. Choose a typeProtanopia, deuteranopia, tritanopia or achromatopsia.
- 3. Fix clashesChange colours that merge, or add labels and patterns.
Worked example
The sample palette has red #E74C3C, green #2ECC71, blue #3498DB, yellow #F1C40F and orange #FF5421. Under Deuteranopia (no green cones), the most common type of colour blindness, the red #E74C3C becomes an olive #9F8F36 and the green #2ECC71 a pale khaki #BAAE77: both lose their red-green difference and are told apart mainly by lightness. The tool also lists pairs whose simulated colours fall closer than a set distance in the OKLab colour space; here it flags the red and the orange #FF5421 as hard to tell apart. That is why charts that use red and green to mean bad and good need labels too.
Upload a screenshot of a dashboard and the whole image is converted, so you can see which lines or segments merge.
How the simulation works
- Colours are converted to linear RGB, multiplied by the matrices published by Machado, Oliveira and Fernandes (2009) at full severity, and converted back.
- Achromatopsia uses relative luminance only, showing the image in greys.
- Large images are scaled to 900 px wide to keep it fast; everything runs in your browser.
A simulation is an approximation. Real colour vision varies by person, and milder forms, where one cone type is shifted rather than missing, are more common than the full types shown. The fix is rarely just new colours: WCAG 1.4.1 asks that colour is not the only way information is shown, so add text labels, icons or patterns too. Check text contrast with the colour code converter and build a balanced palette with the Tailwind colour palette generator.
Frequently asked questions
How common is colour blindness?
Red-green colour vision deficiency is common, especially in men; figures of around 1 in 12 men and 1 in 200 women are widely cited for people of Northern European ancestry, and rates vary by population.
Is my image uploaded?
No. The image is processed on a canvas in this page and never leaves your device.
Is the Color Blindness Simulator free?
Yes, the Color Blindness Simulator is free. The first time you see your first simulation, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.