Protanopia is a type of color vision deficiency caused by the absence or dysfunction of long-wavelength (red) cone cells. People with protanopia have difficulty distinguishing reds and greens, and red appears very dark or black.

What is deuteranopia?

Deuteranopia is caused by absent or non-functional medium-wavelength (green) cone cells. It is the most common form of color blindness, affecting about 1% of males. Reds and greens are confused, similar to protanopia but with different brightness effects.

Tritanopia results from absent short-wavelength (blue) cone cells. It is rare, affecting less than 0.01% of people. Blues and yellows are confused, and the world appears in shades of blue-green and red-orange.

What is achromatopsia?

Achromatopsia (complete color blindness) means no cone cells function normally. Only luminance (brightness) is perceived - everything appears in shades of gray. It affects about 1 in 33,000 people and is often accompanied by light sensitivity.

Color Blindness Simulator

About color vision deficiency

Color blindness (color vision deficiency, CVD) affects approximately 8% of males and 0.5% of females of Northern European descent. The most common forms involve red-green confusion (protanopia and deuteranopia). Tritanopia (blue-yellow) and achromatopsia (complete) are rare.

How the simulation works

Each pixel's RGB values are transformed through a 3×3 simulation matrix derived from Vienot et al. (1999) and Machado (2009) research. The matrix redistributes the color channels to approximate what a person with that condition perceives. Achromatopsia is simulated using standard luminance weights (ITU-R BT.601).

Types of color blindness simulated

Type	Missing cones	Prevalence (males)
Protanopia	Long-wavelength (red)	~1%
Deuteranopia	Medium-wavelength (green)	~1%
Tritanopia	Short-wavelength (blue)	<0.01%
Achromatopsia	All cone cells	~0.003%

Design accessibility guidelines

WCAG 2.1 Success Criterion 1.4.1 (Use of Color) states that color must not be the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. This means:

Error states must use more than just red color (add an icon, text label, or border)
Links in body text must be distinguishable by more than color alone (add underline)
Chart series must use distinct shapes or patterns in addition to different colors
Form field validation must not rely solely on border color changes

Color-safe palette recommendations

When choosing colors for data visualization or UI elements that must be distinguishable by users with CVD:

Safe combinations: blue and orange is one of the most universally safe pairings. Blue and yellow, black and white, and high-contrast purple and yellow are also safe across most CVD types.
Avoid: red and green (the most common confusion pair, affecting ~5% of the male population), red and black at similar brightness, green and brown.
Recommended palettes: Paul Tol's color schemes, ColorBrewer, and IBM's Design Language data visualization palette are all designed with CVD safety in mind.

Testing your own designs

Upload a screenshot of your interface to this simulator and cycle through the CVD modes. If the UI remains usable and all information is distinguishable, your design is accessible.
Browser extensions such as "Colorblinding" (Chrome) or "Sim Daltonism" (macOS app) allow real-time simulation while browsing any website.
When in doubt, add text labels, icons, or patterns alongside color coding. Color should reinforce meaning, not be the sole carrier of it.