Not all colour blindness is the same: a guide to protanopia, deuteranopia and tritanopia

In the world of digital accessibility, the topic of color blindness is often reduced to simple contrast ratios. But in 2026, we know better: color perception is individual and complex. For millions of people worldwide, the internet is not a colorful place, but a challenge of grayscale or distorted hues. To truly meet the requirements of the WCAG and the BFSG, we must understand that color vision deficiency has many different forms.

The different facets of color vision deficiency

Protanopia and protanomaly (red blindness / red weakness)

People with protanopia lack cone cells for long-wavelength light. This means that the color red is barely or not at all perceptible to them. In practice, red and green tones are often confused, which is particularly problematic for error messages in forms. An optimized UX (user experience) must ensure that information is not conveyed by color alone.

Deuteranopia and deuteranomaly (green blindness / green weakness)

This is the most common form of color vision deficiency. Affected users have difficulty distinguishing green tones from red hues. Since many websites use green to indicate “success” and red to indicate “errors,” this creates significant barriers. Intelligent accessibility therefore relies on additional symbols or text descriptions to guarantee usability for everyone.

Tritanopia and tritanomaly (blue blindness / blue weakness)

Tritanopia is much rarer, but just as limiting for those affected. In this case, perception of blue and yellow light is impaired. Blue often appears green, and yellow is hardly distinguishable from violet. In modern web design, these contrast pairs must be taken into account when choosing colors.

Why intelligent contrast filters are the solution

Standard solutions often offer only a simple high-contrast mode. Modern tools like MH-Accessibility Pro go a step further. With a dedicated color vision deficiency filter, users can adjust the color rendering of the entire website in real time to match their specific visual impairment.

In addition, an intelligent contrast feature helps by not merely inverting colors, but by optimizing readability through adjustments to color saturation and brightness. This not only increases inclusion, but has been proven to improve conversion rates in online shops, as users no longer have to give up due to unreadable checkout buttons.

Leveraging synergies with other accessibility needs

Accessibility is rarely an isolated issue. Users with visual impairments often benefit from features originally developed for other needs. For example, a clear focus indicator helps users locate clickable elements even when color contrast is difficult to perceive individually.

Just as we described for typography in our article Dyslexia and digital accessibility, usability is also the top priority when it comes to color. Anyone looking to reduce visual overstimulation should also consider features such as monochrome mode to create a calmer working environment—a topic we also explore in detail in ADHD on the web – how to stop visual distractions.

Conclusion: Accessibility in 2026

Anyone operating a website today can no longer avoid professional inclusion. It is no longer just about preventing legal warnings, but about enabling access to information for everyone. With tools like the Accessibility-Tester, you can already assess where your site stands today, and with features such as the statement generator, you can transparently document your progress.

Make your website visible to everyone. Discover how MH-Accessibility Pro improves perception for all target groups. View pricing