Color Blindness Simulator

What Is Colour Blindness?

Colour blindness (colour vision deficiency, CVD) is the reduced ability to perceive differences between colours that are apparent to most people. The human eye has three types of photoreceptor cones: L-cones (sensitive to long/red wavelengths), M-cones (medium/green), and S-cones (short/blue). When one or more cone types are absent or have reduced sensitivity, the affected person experiences a limited colour gamut.

Approximately 8% of men and 0.5% of women worldwide have some form of colour vision deficiency. The most common forms are red-green colour blindness (protanopia and deuteranopia), which are X-linked genetic conditions.

Types of Colour Vision Deficiency

• Protanopia — Complete absence of L-cones (red-sensitive). Affects about 1% of men. Reds appear dark and cannot be distinguished from green.
• Deuteranopia — Complete absence of M-cones (green-sensitive). The most common severe form, affecting about 1% of men. Green and red look similar.
• Tritanopia — Complete absence of S-cones (blue-sensitive). Very rare (1 in 10,000). Blue appears green; yellow appears pink or violet.
• Protanomaly / Deuteranomaly / Tritanomaly — Anomalous trichromacy where the respective cone type is present but with shifted or reduced sensitivity. These are milder forms and are more common than their anopic counterparts.
• Achromatopsia — Complete colour blindness; only rods are functional. Extremely rare (1 in 30,000). Everything is seen in greyscale.
• Achromatomaly — Partial achromatopsia with residual, greatly reduced colour perception.

How This Simulator Works

This tool uses published colour transformation matrices based on the algorithms by Vienot et al. (1999) and Brettel et al. (1997). The simulation pipeline is:

1. Convert the sRGB hex colour to linear-light RGB values (gamma expansion).
2. Apply a 3×3 transformation matrix that maps the linear RGB to the simulated colour space for the given deficiency type.
3. For anomaly types (protanomaly, deuteranomaly, tritanomaly), interpolate 50% between the original and the full deficiency simulation.
4. For achromatopsia, convert to luminance-weighted greyscale (0.2126R + 0.7152G + 0.0722B).
5. Apply gamma compression (sRGB encoding) and convert back to a hex value.

Why Design for Colour Blindness?

Designing with colour accessibility in mind ensures your UI, data visualisations, charts, and images are usable by everyone. Best practices include: not relying solely on colour to convey information, using patterns or labels in addition to colour, choosing palettes with sufficient contrast, and testing with a colour blindness simulator during the design phase.

Use the related Color Contrast Checker to verify that your colour combinations also meet WCAG 2.1 contrast requirements for text readability.