Tritanomaly · tritan anomalous trichromacy
Tritanomaly (blue-yellow weak)
Weakened S-cone function blurs the distinction between blue and green, and between yellow and pink. The congenital form is very rare; acquired forms are more common.
- Altered cones
- Reduced S function
- Inheritance
- Autosomal dominant · often acquired
- Prevalence
- Congenital form very rare
- Common mimics
- Night mode, yellow lighting
How it works
In tritanomaly, S-cone function is only partly preserved, weakening color discrimination along the blue-yellow direction. Congenital tritan defects vary widely in severity even among people with the same gene variant, so the line between tritanopia and tritanomaly is often blurry.
Acquired blue-yellow defects can occur with yellowing of the lens (aging, cataract), glaucoma, diabetic retinopathy, and macular disease, and the two eyes may be affected to different degrees.
Environments with less short-wavelength light — warm incandescent-style lighting, screens in night mode — temporarily reduce blue-yellow discrimination even in normal color vision.
What you see
The boundary between a blue sky and a teal sea, the difference between yellow and white, and distinctions among purples all become fuzzy. Colors may also seem slightly washed out overall.
The table below uses a 60% severity simulation.
| Color | Normal vision | Tritanomaly (blue-yellow weak) |
|---|---|---|
| Red | #D7263D | #E00037 |
| Orange | #F28C28 | #FB8359 |
| Yellow | #F2CD37 | #F9C681 |
| Green | #2E9E44 | #1B9D6B |
| Teal | #1A9E9A | #00A09B |
| Blue | #2F6BD8 | #0077BE |
| Purple | #7E3FB2 | #7C4A99 |
| Pink | #E86FA6 | #EF6D97 |
| Brown | #8B5A2B | #90563F |
| Gray | #8C8C8C | #8C8C8C |
Simulation: Machado, Oliveira & Fernandes (2009) matrices at 60% severity. Results may differ from reality depending on your monitor and individual differences.
How common is it?
Congenital blue-yellow defects are very rare, affecting fewer than 1 in 10,000 people (MedlinePlus Genetics). Acquired, age-related decline in blue-yellow discrimination, by contrast, is far more common.
Exact prevalence depends heavily on how it is measured, so estimates vary from study to study.
Easily confused colors
- Blue ↔ green ↔ teal
- Yellow ↔ white, pale yellow ↔ pale pink
- Navy ↔ black (in dim light)
Everyday tips
- Before an online check, turn off night mode, blue light filters, and any “warm” color temperature setting.
- If your color discrimination has changed recently, see an eye doctor first — there may be a treatable cause such as cataract or glaucoma.
- Checking colors under bright, daylight-type lighting makes them easier to tell apart.