Color Blindness Simulator
Fast, secure, client-side utility running entirely in your browser with zero server dependencies.
Color Blindness Simulator
Simulate how people with red-green, blue-yellow, and complete color blindness perceive your brand colors and UI contrast ratios.
Interactive Color Vision Deficiency (CVD) Simulation
Enter foreground and background colors to test whether your palette maintains sufficient contrast under Protanopia (red-blind), Deuteranopia (green-blind), and Tritanopia (blue-blind).
Visual Perception Previews
Color Blindness Simulator - Protanopia, Deuteranopia & Tritanopia Preview: Free Color Blindness Simulator tool: simulate color combinations across protanopia, deuteranopia, tritanopia, and achromatopsia to verify WCAG contrast.
How to Use the Color Blindness Simulator
Input Text & Background Colors
Provide your UI element hex color values or choose a preset color challenge (such as red-on-green).
Simulate Color Vision Deficiencies
The tool applies standardized Brettel LMS transformation matrices simulating Protanopia (red-blind), Deuteranopia (green-blind), and Achromatopsia.
Evaluate Perceived Contrast Ratios
Compare contrast ratios under each vision condition against the WCAG 2.2 Level AA 4.5:1 threshold.
Refine Color Luminance Differences
Adjust hue and lightness to ensure text remains clearly legible even when colors shift to yellow-brown or gray tones.
Comprehensive Guide: Color Blindness Simulator
Approximately 8% of men and 0.5% of women worldwide—over 300 million people—live with some form of color vision deficiency (CVD). The vast majority have red-green color blindness (Deuteranopia and Protanopia), while smaller percentages experience blue-yellow color blindness (Tritanopia) or complete absence of color perception (Achromatopsia).
Under WCAG 1.4.1 (Use of Color), color must not be used as the sole visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. For instance, displaying an error message solely with red text (without an accompanying icon, bold weight, or explicit "Error:" prefix) leaves red-blind users unable to discern that an error has occurred.
Red-green color combinations are particularly vulnerable to total contrast collapse. To a person with normal vision, bright red text (#dc2626) on a green background (#16a34a) appears intensely vibrant due to opposing chromatic wavelengths. However, in the eyes of a person with deuteranopia or protanopia, both red and green photons map to identical muddy brownish-yellow hues, reducing perceived visual contrast to near zero.
Designing accessible color systems requires prioritizing luminance contrast over chromatic contrast. While colors may appear distinct due to hue differences, true accessibility depends on relative photopic luminance (lightness vs darkness). Testing your palette with color blindness simulation matrices guarantees that your user interfaces remain clear, trustworthy, and readable across all optical conditions.
Key Features & Capabilities
Brettel LMS Transformation Matrix
Applies peer-reviewed physiological color simulation algorithms developed by the international color vision community.
Red-Green & Monochromatic Simulation
Simulates Deuteranopia (green-blind), Protanopia (red-blind), and Achromatopsia (complete monochrome).
WCAG 1.4.1 Use of Color Compliance
Ensures crucial UI information and error alerts never depend exclusively on chromatic hue cues.
Dynamic Contrast Degradation Math
Calculates the real-time drop in numerical contrast ratios caused by optical cone deficiencies.
Side-by-Side Visual Previews
Renders simulated buttons and text blocks simultaneously for intuitive design system reviews.
Confidential Client-Side Execution
Calculates all RGB-to-LMS matrices in browser memory with zero network overhead.
Frequently Asked Questions
Deuteranopia and Deuteranomaly (green-weakness or green-blindness) is the most widespread, affecting roughly 6% of males. Combined with Protanopia (red-blindness), red-green color vision deficiency affects roughly 8% of men and 0.5% of women worldwide.
The 4.5:1 contrast ratio accounts for natural human vision variance, including age-related vision loss (the lens of the human eye yellows and clouds with age) and color vision deficiencies. Colors that appear separated by hue to normal trichromats often lose distinctiveness under color blindness, making high luminance contrast essential.
Never rely on color alone to differentiate lines or slices in a graph. Pair distinct colors with patterns (e.g. dashed lines vs dotted lines), distinct marker shapes (circles, squares, triangles), direct text labels, and high luminance differences.
Achromatopsia is complete color blindness resulting from the total absence of functioning retinal cone photoreceptors. Individuals with achromatopsia see the world purely in shades of gray, black, and white, making luminance contrast the only way they can distinguish content.
No. Color blind glasses use optical notch filters to increase the separation between red and green wavelengths in natural outdoor light, but they do not cure color blindness and have limited effectiveness on digital RGB screens. Websites must be engineered accessibly.