Color Blindness Simulator: Protanopia, Deuteranopia & WCAG Checker

Understanding Color Blindness and Web Accessibility

Color blindness, or color vision deficiency, is the decreased ability to see color or differences in color. It affects approximately 8% of men and 0.5% of women across the United States and worldwide. The most common forms — Protanopia and Deuteranopia — make it difficult or impossible to distinguish between red and green, which are two of the most frequently used colors in web interfaces for success/error states, charts, and navigation.

Under the Web Content Accessibility Guidelines (WCAG), websites must not rely on color alone to convey information. Using a color blindness simulator ensures your designs are accessible to this significant user base, meeting both ethical standards and legal compliance requirements such as the Americans with Disabilities Act (ADA). Our tool helps you identify problematic color combinations before they ship, saving you costly redesigns and protecting your audience.

Beyond compliance, accessible design is simply better design. When your interface works for people with color vision deficiencies, it works better for everyone — including users in bright sunlight, on low-quality displays, or in high-stress environments where visual clarity matters most. If you're building a new palette, try our color palette generator first, then test it here.

How to Use This Color Blindness Simulator

Testing your UI for accessibility doesn't have to be complicated. This tool walks you through the entire process in a few simple steps — no design expertise required.

1. Input Your Palette: Enter up to five HEX color codes in the input fields above. You can also click "Random Palette" to generate a starting point or "Load Example" to see a pre-built palette in action.
2. Choose Severity: Select Normal, Mild, Moderate, or Severe to control how strongly the simulation transforms your colors. This helps you test edge cases and partial vision deficiencies.
3. Run the Simulation: Click "Simulate" to generate views for Protanopia, Deuteranopia, Tritanopia, and Achromatopsia. Each preview shows a gradient of your colors as seen through that type of color vision deficiency.
4. Check Contrast: Scroll down to the Contrast Checker and enter your foreground and background colors. The tool instantly calculates the contrast ratio and tells you whether it passes WCAG AA (4.5:1) or AAA (7:1) standards.
5. Review the Comparison Table: The color comparison table shows each of your original colors side-by-side with their simulated versions, making it easy to spot which specific colors become indistinguishable.

Once you've identified problematic colors, adjust your palette and re-test. You can also explore our gradient generator to create smooth, accessible color transitions.

Who Uses a Color Blindness Simulator?

This tool is built for anyone who creates visual content that needs to reach a broad audience. Here are some of the most common use cases:

• UI/UX Designers: Verify that your design system's color tokens are distinguishable across all vision types before handing off to developers. Pair this with our contrast checker for a complete accessibility audit.
• Front-End Developers: Test your CSS color variables, Tailwind theme colors, or component libraries to make sure your live interface is perceivable by all users.
• Data Visualization Engineers: Charts, graphs, and dashboards often rely on color to differentiate data series. A simulator helps you pick a palette that remains readable when reds and greens merge.
• Product Managers: Validate that your product's status indicators — success (green), warning (yellow), error (red) — are not relying on color alone, which is a common WCAG violation.
• Educators & Content Creators: Ensure your slides, infographics, and teaching materials are accessible to students with color vision deficiency.

Benefits of Testing for Color Accessibility

• Reach a Wider Audience: With 300 million people worldwide experiencing color vision deficiency, accessible colors directly translate to more users who can use your product without frustration.
• Avoid Legal Risk: Web accessibility lawsuits under the ADA and similar laws are rising every year. Color-related violations are among the most common complaints.
• Improve Overall Usability: High-contrast, color-independent designs are easier to read in poor lighting, on small screens, and for aging populations — benefits that extend far beyond color-blind users.
• Build Brand Trust: Companies that invest in accessibility signal that they care about all their users, which strengthens brand loyalty and reputation.
• Save Time and Money: Catching accessibility issues during the design phase is dramatically cheaper than fixing them after launch. A quick simulation now prevents expensive redesigns later.

Design Tips for Accessibility

• Don't Rely on Color Alone: Use icons, patterns, or text labels to convey meaning alongside color cues.
• High Contrast: Ensure sufficient contrast ratios — WCAG AA requires 4.5:1 for normal text and 3:1 for large text.
• Avoid Problematic Combos: Red/green and blue/black combinations are particularly difficult for people with color vision deficiencies.
• Use a Simulator: Always test your designs with a simulator tool like this one before shipping.
• Test with Real Users: Automated tools catch many issues, but user testing with people who have color vision deficiency reveals problems simulators might miss.

Why I Built This Tool

A few years ago, I shipped a dashboard at work that used red and green status badges to indicate success and failure. I thought it looked great — until a colleague mentioned, casually, that he couldn't tell the difference between the two. He was one of the 8% of men with red-green color blindness, and my "intuitive" design was completely invisible to him.

That moment stuck with me. I started looking for a quick way to test my colors before committing to them, and while there were some tools out there, most were clunky, required uploads, or only handled one type of color blindness at a time. I wanted something fast — paste in my HEX codes, see all the simulations side by side, and check contrast ratios without switching tabs.

So I built this. It's the tool I wish I had on that project. I hope it saves you from making the same mistake I did — and that it makes designing for everyone just a little bit easier. If you find it useful, consider exploring the other free tools on DevPalettes.

Frequently Asked Questions