Tritanopia
(Blue-Yellow Color Blindness)
Tritanopia is a rare blue-yellow deficiency (about 0.01%). Blues can look greenish and yellows pink or grey. The milder form is tritanomaly.
Take the free 18-plate tritanopia test below (Ishihara-style screening, not a clinic diagnosis).
Free Online Color Blindness Test
Take our free Ishihara color blind test to check for red-green color blindness, deuteranopia, protanopia, and tritanopia. Get instant results with our scientifically-designed 18-plate color vision screening test. No registration required.
- Disable dark mode and blue-light filters (Night Shift, f.lux)
- Set screen brightness to at least 80%
- Ensure you are in a neutral lighting environment
- View screen from a normal reading distance
What Is Tritanopia Color Blindness?
Tritanopia is a form of color vision deficiency (CVD) caused by the absence or malfunction of the short-wavelength (S) cone cells in the retina. These cones are responsible for perceiving blue light. Without them, the blue-yellow channel of color vision is effectively eliminated.
People with tritanopia typically perceive blues as greenish, yellows as pink or red, and have difficulty distinguishing between blue-green and red-pink. Unlike red-green color blindness, tritanopia affects men and women equally but it is significantly rarer, affecting approximately 0.01% of the population.
Tritanopia vs. Tritanomaly
Tritanopia (complete blue blindness) is the severe form. Tritanomaly is the partial form, where S-cones are present but underperform causing similar but less extreme color confusion. Both are classified as blue-yellow color vision deficiencies and can be detected with the same screening plates.
Symptoms and Everyday Challenges
- Difficulty distinguishing blue from green
- Yellow appears pinkish or red
- Purple appears reddish
- Night sky appears greenish rather than dark blue
- Ocean and sky colors appear similar to grass
In practical terms, people with tritanopia may struggle with: traffic signal reading in some lighting conditions, selecting matching clothing, reading color-coded charts and graphs, and interpreting maps that use blue and green together.
Causes of Tritanopia
Tritanopia can be congenital (present from birth) or acquired. Congenital tritanopia is caused by a mutation in the OPN1SW gene on chromosome 7. Acquired tritanopia can result from conditions affecting the macula, optic nerve, or retina including glaucoma, cataracts, and age-related macular degeneration.
How to Test for Tritanopia
The standard clinical test for tritanopia uses the Farnsworth-Munsell D-15 test or the City University Colour Vision Test. Online, Ishihara-style plates can screen for tritanopia alongside deuteranopia and protanopia in the same session.
Our free color blind test includes tritanopia-specific plates. Take the 18-plate test to screen for all major CVD types at once.
Designing for Tritanopia
Since tritanopia is far less common than red-green color blindness, it is often overlooked in accessibility audits. However, WCAG 2.2 Success Criterion 1.4.1 (Use of Color) applies to all CVD types. Key design guidelines:
- Avoid using blue and yellow as the only differentiating colors in charts or diagrams
- Add text labels or patterns as redundant cues alongside color
- Test your UI with our color blind simulator under "Tritanopia" mode
- Ensure WCAG contrast ratios are met regardless of hue
FAQ
What is tritanopia?
Tritanopia is blue-yellow color blindness caused by absent or non-functional S-cones. Blues appear greenish and yellows can look pink or grey.
How do people with tritanopia see?
Blue-yellow discrimination is lost. Sky, bananas, and purple vs red can collapse. Red-green discrimination is relatively spared compared with deuteranopia.
How do I test for tritanopia online?
Use the free 18-plate Ishihara-style test on this page. Results appear in under two minutes with no signup. Confirm unusual patterns with an eye-care professional.
Is tritanopia the same as tritanomaly?
No. Tritanomaly is partial blue-yellow weakness (S-cones present but shifted). Tritanopia is the complete form. Take the dedicated tritanomaly test if you want the partial-form page.
How rare is tritanopia?
About 0.01% of people. Unlike red-green CVD it is not X-linked, so men and women are affected similarly.
Test yourself or your designs now
Our free test screens for tritanopia, deuteranopia, protanopia, and achromatopsia in under 2 minutes.