Protanopia Simulation: See What Red-Blind People See

Protanopia is a form of color vision deficiency caused by the complete absence of red (long-wavelength) cone photoreceptors in the retina. It is one of the two main types of red-green color blindness, along with deuteranopia. People with protanopia see the world with only two types of cones — medium-wavelength (green) and short-wavelength (blue) — instead of the usual three. This condition affects roughly 1% of males and is extremely rare in females due to its X-linked recessive inheritance pattern.

The most significant effect of protanopia is that red colors appear much darker and shift toward brown, olive, or gray tones. Greens also shift, often appearing yellowish or tan. Because both red and green are perceived through overlapping channels, many red-green combinations become nearly indistinguishable. Blues and yellows remain relatively unaffected, which is why blue-yellow contrast is often recommended for colorblind-friendly design. Orange and red, which differ primarily in their red component, can look almost identical to someone with protanopia.

While protanopia involves the complete absence of red cones, protanomaly is a milder condition where red cones are present but have a shifted sensitivity. People with protanomaly can still perceive some red-green differences, though with reduced accuracy. Protanomaly is about three times more common than protanopia, affecting roughly 1% of males compared to about 1% for protanopia. Both conditions fall under the broader category of protan color vision deficiency, but protanomaly typically has less impact on daily activities.

People with protanopia face challenges in many everyday situations. Traffic lights can be difficult — red and amber signals may appear similar, though position helps with identification. Cooking meat to the right color is harder since the transition from pink to brown is muted. Choosing matching clothing, reading color-coded charts, and distinguishing ripe from unripe fruit are all common struggles. Many people with protanopia develop compensating strategies, such as relying on brightness differences, labels, or context clues rather than color alone.

When designing interfaces, charts, or signage for protanopia accessibility, avoid relying solely on red-green distinctions. Use high-contrast combinations like blue and orange, or add patterns, labels, and icons alongside color coding. Data visualizations should use colorblind-safe palettes — tools like Color Oracle and Coblis can simulate how designs look to people with protanopia. The Web Content Accessibility Guidelines (WCAG) recommend never using color as the sole means of conveying information, which benefits all users with color vision deficiency.