How to Test Colors for Color Blindness in Your Browser

To test whether your colors work for color-blind users, enter a HEX code into the Color Blindness Simulator and compare the original swatch with four simulated versions — protanopia, deuteranopia, tritanopia and achromatopsia. If two important colors look nearly identical in any simulation, adjust one of them. The whole check takes seconds and runs entirely in your browser, so nothing is uploaded and there is no account to create.

Color vision deficiency (CVD) affects roughly 1 in 12 men and 1 in 200 women, which means most public-facing designs are seen by someone who cannot separate certain hues. This tutorial walks through the tool from first color to final decision.

What the simulator actually does

The tool takes the color you enter and applies standard color-transform matrices — the same mathematical models researchers use to approximate dichromatic vision. It renders five swatches side by side: your original color plus how it appears under the four most common types of color blindness. Each simulated swatch comes with its own resulting HEX code, so you can see numerically how far a color shifts.

The four simulations are:

• Protanopia — reduced sensitivity to red light.
• Deuteranopia — reduced sensitivity to green light (the most common type).
• Tritanopia — a rarer blue-yellow deficiency.
• Achromatopsia — total color blindness, where only brightness remains.

Step-by-step: testing a color

1. Enter your color. Type or paste a HEX code, or use the picker to select the exact shade from your design.
2. Scan the simulated swatches. Look across protanopia, deuteranopia, tritanopia and achromatopsia to see how the color drifts under each.
3. Read the simulated HEX values. These tell you precisely where each color lands so you can spot collisions between two states.
4. Adjust and re-test. If a success green and an error red converge under deuteranopia, nudge one toward a different lightness and run the check again.

Testing a pair, not just one color

The most useful check is comparing two colors that must stay distinct — a chart's two series, a form's valid and invalid states, or a map's legend keys. Run each color through the simulator and compare the achromatopsia result in particular: because it strips hue entirely, it reveals whether your colors differ in brightness. If they look identical in grayscale, they will be hard for many CVD users too.

Simulation	What it reveals	Watch for
Protanopia	Red-channel loss	Reds dulling toward brown or gray
Deuteranopia	Green-channel loss	Green vs. red collapsing together
Tritanopia	Blue-yellow loss	Blue vs. green confusion
Achromatopsia	Lightness only	Two colors sharing the same brightness

Why in-browser and private matters

Because every simulation is computed locally with matrix math, your brand colors and unreleased mockups never leave your machine. There is no upload step, no sign-in, and the tool keeps working offline once the page has loaded — handy on a locked-down work network or a flight.

Try the Color Blindness Simulator — free and 100% in your browser.

FAQ

Do I need to test every color in my design?

No — focus on colors that carry meaning on their own, such as status indicators, chart series, and links. Decorative colors that are backed up by text or icons rarely cause problems.

Which simulation should I trust most?

Deuteranopia and protanopia cover the vast majority of color-blind users, so treat those as your baseline. Use achromatopsia as a strict brightness test that catches the widest range of issues at once.

Can I paste a HEX with or without the hash?

Either works. Enter a six-digit HEX like #3366cc or 3366cc, and the tool normalizes it before running the transform.

Does passing the simulator guarantee accessibility?

It is a strong first-pass check, not a certificate. Simulations estimate perception, and real CVD experiences vary, so always pair color choices with text labels, icons or patterns for anything critical.

Related free tools

• Contrast Checker — verify text and UI meet WCAG contrast ratios.
• Color Palette Generator — build palettes with built-in variety.
• Color Name Finder — put a readable name to any HEX.
• Color Picker — grab exact HEX and RGB values.

Built by ByteVancer

ByteTools is a free product of ByteVancer, a software and web development studio that builds web apps, SaaS platforms and custom software with accessibility baked in. If you need a team that treats inclusive design as a requirement rather than an afterthought, explore what ByteVancer can build for you.