Protanopia is a form of red-green color blindness caused by absent or non-functional long-wavelength (L) cone cells. Affected individuals cannot distinguish reds from greens and perceive red hues as very dark. It affects roughly 1% of men.

What is deuteranopia?

Deuteranopia is the most common type of color blindness, affecting about 1–2% of men. It results from absent medium-wavelength (M) cone cells, causing difficulty distinguishing red and green hues, though brightness perception is largely intact.

Tritanopia is a rare blue-yellow color blindness caused by absent short-wavelength (S) cone cells. It affects less than 0.01% of people and causes confusion between blue and green, and between yellow and violet.

How are the simulated colors calculated?

The tool linearizes the sRGB channels, applies the Machado et al. (2009) matrix for complete protanopia, deuteranopia, or tritanopia, clips the result to the displayable range, and converts it back to sRGB. The matrices model the corresponding color-vision deficiency while preserving neutral colors such as white and gray.

Why can a color pair pass original WCAG but fail for color-blind users?

Color vision deficiencies change how luminance is distributed across hues. A red text on green background may have adequate contrast in normal vision but become nearly identical in luminance once both colors shift under protanopia, dropping the contrast ratio well below 4.5:1.

Does passing this checker guarantee full accessibility?

Passing WCAG contrast under all three simulations is a strong signal, but full accessibility also requires sufficient contrast in the original colors, adequate font size, and not relying solely on color to convey information (WCAG 1.4.1).

Color Blind Safe Checker

Enter two colors to see how they appear under three types of color blindness, with WCAG contrast ratios for each simulated view.

Foreground (Text) Color

Background Color

Original Colors — Contrast

Sample Text

—

AA — AAA —

Protanopia (red-blind, ~1% of men)

Original

Text

Simulated

Text

Simulated contrast

—

AA — AAA —

Simulated: fg — / bg —

Deuteranopia (green-blind, ~1–2% of men)

Original

Text

Simulated

Text

Simulated contrast

—

AA — AAA —

Simulated: fg — / bg —

Tritanopia (blue-blind, rare)

Original

Text

Simulated

Text

Simulated contrast

—

AA — AAA —

Simulated: fg — / bg —

Summary

Enter two colors to see how they appear under three types of color blindness, with WCAG contrast ratios for each simulated view.

How it works

Enter or pick a foreground color and a background color using the hex inputs or color pickers.
The tool applies three LMS-space color vision deficiency matrices: protanopia, deuteranopia, and tritanopia.
Each simulation produces a transformed foreground and background color that represents what a color-blind user perceives.
The WCAG 2.1 contrast ratio is computed for each simulation pair and compared against AA (4.5:1) and AAA (7:1) thresholds.
Side-by-side swatches and text previews let you visually compare the original and simulated views.
Use the results to identify which color combinations fail under specific vision types and adjust accordingly.

Use cases

Verify that UI color pairs remain distinguishable for red-green color-blind users.
Test brand color combinations for accessibility before publishing design tokens.
Audit data visualization palettes that must convey meaning without relying on color alone.
Check button/label contrast for all three major types of color vision deficiency.
Satisfy WCAG 2.1 Level AA requirements for users with color vision impairments.
Educate design teams on how specific colors are perceived differently by color-blind users.
Validate link-vs-body-text color pairs that often fail for deuteranopes.
Run quick pre-launch accessibility checks for high-traffic pages.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu

Color Blind Safe Checker

Use the Color Blind Safe Checker

Original Colors — Contrast

Protanopia (red-blind, ~1% of men)

Deuteranopia (green-blind, ~1–2% of men)

Tritanopia (blue-blind, rare)

Summary

How it works

Use cases

Frequently Asked Questions