Deuteranomaly · deutan anomalous trichromacy
Deuteranomaly (green-weak)
The most common type of color vision deficiency. M-cone sensitivity is shifted toward L, weakening discrimination among greens and related colors.
- Altered cones
- M shifted toward L (M′)
- Inheritance
- X-linked recessive
- Prevalence
- Men ~4.6% · women ~0.4%
- Severity
- Wide range, from very mild to strong
How it works
Deuteranomaly is a form of anomalous trichromacy in which the M-cone photopigment is shifted toward L wavelengths. The closer the L and M sensitivity curves get, the smaller the difference between the two signals, and the weaker the discrimination of greens and reds.
The X chromosome carries one L photopigment gene followed by several M photopigment genes in a row, and hybrid genes formed by mixing within this array are a common cause.
The sense of red brightness is usually normal, and depending on severity, many people go through life hardly noticing it.
What you see
Vivid primary colors are mostly distinguishable, but similar tones — yellow-green/yellow/orange, green/brown, purple/blue — get confused, especially in small dots and thin lines.
The table below uses a 60% severity simulation. In the simulator, lower the severity to see mild deuteranomaly, or raise it to approach deuteranopia.
| Color | Normal vision | Deuteranomaly (green-weak) |
|---|---|---|
| Red | #D7263D | #9E6E37 |
| Orange | #F28C28 | #CEA626 |
| Yellow | #F2CD37 | #EDD23D |
| Green | #2E9E44 | #858D49 |
| Teal | #1A9E9A | #768F9B |
| Blue | #2F6BD8 | #006AD7 |
| Purple | #7E3FB2 | #4558B0 |
| Pink | #E86FA6 | #B295A4 |
| Brown | #8B5A2B | #7A652B |
| 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?
It is reported in about 4.6% of men and about 0.4% of women of European ancestry, accounting for more than half of all red-green deficiencies (Sharpe et al., 1999).
The rate in women is higher than for other types because the more common a trait is, the more likely it is that both X chromosomes carry it.
Easily confused colors
- Yellow-green ↔ yellow ↔ orange, green ↔ brown
- Blue-green ↔ gray, purple ↔ blue
- Pink ↔ light gray/beige
Everyday tips
- When you see red-green pairs in data visualizations or maps, check the legend's shapes, patterns, or direct labels as well.
- If you're a designer, check your work in the simulator and refer to the colorblind-friendly palettes guide.
- People with mild deuteranomaly often miss only the dot plates with the smallest color differences. If your results are inconsistent, try again on another device.