Free Color Blindness Simulator — Test Your Colors for Accessibility

Color Blindness Simulator: Design Colors That Work for Everyone

Roughly 1 in 12 men and 1 in 200 women have some form of color vision deficiency — meaning a meaningful share of any website's audience may not see your color choices the way you designed them. A color blindness simulator lets you preview your palette the way those users actually experience it, before a color-only design decision becomes an accessibility problem.

This guide explains the main types of color blindness and how to test your colors against them.

The Main Types of Color Vision Deficiency

Color blindness isn't one single condition — different types affect sensitivity to different parts of the color spectrum:

Deuteranopia and protanopia are collectively known as "red-green color blindness" and together affect roughly 8% of men of Northern European descent, making them by far the most common forms designers need to account for.

Why "Just Use Red and Green" Is a Common Accessibility Mistake

Red and green are the most intuitive colors for "bad" and "good" — error and success states, decrease and increase, stop and go. But for someone with red-green color blindness, those two colors can be difficult or impossible to reliably distinguish. If color is the *only* signal carrying that meaning, a meaningful portion of users lose access to that information entirely.

The fix isn't to avoid red and green — it's to never rely on color alone. Pairing color with an icon, a label, a pattern, or a shape means the information still gets through even if the color difference doesn't.

How to Test Your Colors Online (Step by Step)

Using the ToolzGo Color Blindness Simulator takes a few seconds:

• •Go to toolzgo.com/tools/design-tools/color-blindness-simulator
• •Add one or more HEX colors — your brand palette, or a chart's color scheme
• •View each color transformed for protanopia, deuteranopia, tritanopia, and achromatopsia side by side
• •Compare the simulated swatches against your originals to spot colors that become too similar

What to Do If Two Colors Look Too Similar

If a simulation shows two colors converging under a particular deficiency, the most reliable fix is to increase the difference in **lightness**, not just hue. Two colors can have very different hues but similar lightness, which is often what makes them hard to distinguish under certain color vision deficiencies — adjusting lightness (not just picking a "different" color) tends to be the more robust fix.

Frequently Asked Questions

Q: What is the most common type of color blindness?

A: Deuteranopia (reduced sensitivity to green) and protanopia (reduced sensitivity to red) are the most common, together affecting about 8% of men of Northern European descent.

Q: Why shouldn't I use only red and green to show status?

A: People with red-green color blindness (protanopia/deuteranopia) may not reliably distinguish red from green, so critical states like "error" vs "success" should also use icons, labels, or distinct shapes.

Q: Does this simulator diagnose color blindness in a person?

A: No — it simulates how a given color would appear to someone with a color vision deficiency, as a design accessibility check. It does not test or diagnose an individual's vision.

Q: Should I test my entire palette, or just problem colors?

A: Testing your entire palette is best practice, especially any colors used to convey meaning (status indicators, chart series, form validation) rather than purely decorative ones.

Pair this with the ToolzGo WCAG Contrast Checker to cover both color-vision accessibility and general text legibility, or build your palette from the ground up with the Color Palette Generator.

Test your colors for color-blind accessibility now.