Colour Blindness Simulator

About 1 in 12 men and 1 in 200 women see colour differently, most often finding reds and greens hard to separate. Colour Blindness Simulator shows you what they see. Load a chart, a map, a game screen, a website mock-up or a photo, pick a type, and drag the divider across to compare it with the original, or view all eight types in one grid.

The second tab answers a quicker question: will these two colours work together? Pick any pair, such as the red and green in a profit-and-loss chart, and the tool shows both colours as each type sees them, with a measured difference and a plain verdict like “Easy to mix up”. No picture handy? The built-in test chart has a rainbow strip, chart colours, traffic lights, a bar chart and a dot plate.

The maths comes from peer-reviewed research, not guesswork: Viénot, Brettel and Mollon (1999) for protanopia and deuteranopia, Brettel, Viénot and Mollon (1997) for tritanopia, and Machado, Oliveira and Fernandes (2009) for the milder “-anomaly” types, with a severity slider. Everything runs in your browser; your images are never uploaded.

1. On the “Picture” tab, tap “Choose an image”, paste a screenshot, or press “Use the test chart”.
2. Pick a type of colour blindness. For the “-anomaly” types, set “Severity”.
3. Choose a view: “Slider” to drag between original and simulated, “Side by side”, or “All types”.
4. Press “Download simulated image” to save the chosen type at full size.
5. To test two colours, open “Colour pair check”, pick or type them, or try one of the classic pairs.

• Eight types: protanopia, deuteranopia, tritanopia, protanomaly, deuteranomaly, tritanomaly, achromatopsia and blue-cone monochromacy.
• Severity from 10% to 100% for the three “-anomaly” types, using Machado et al.’s published table.
• Three views: draggable before/after slider, side by side, and a grid of all eight types at once.
• Colour pair check with CIEDE2000 difference, a plain verdict for every type and the WCAG brightness contrast ratio.
• Six classic problem pairs to try, plus colour pickers and hex codes.
• Built-in test chart, drawn on the spot, for a quick look without a file.
• Downloads the simulation at the picture’s full resolution.
• Opens JPG, PNG, HEIC, WebP, AVIF, TIFF, GIF, BMP, SVG and ICO.

• Start with deuteranomaly at 60%: it is the most common type. If your chart still reads well there and under protanopia, most viewers will be fine.
• Don’t rely on colour alone. Labels, patterns, icons or a clear lightness difference (contrast of 3:1 or more) work for every type.
• Use the “All types” grid for a quick health check of a whole dashboard or poster.
• Simulations show the typical case. Real people vary, and screens differ, so treat it as a strong guide rather than an exact copy of someone’s eyes.
• Blue-cone monochromacy is a rough approximation based on night-vision brightness; the other types follow the published models.