What is blue-yellow color blindness?

It is tritan deficiency — a weak or missing blue (S) cone that makes blue hard to tell from green and yellow hard to tell from pink or violet. It is much rarer than red-green color blindness and affects men and women about equally.

What is the difference between tritanomaly and tritanopia?

Tritanomaly is the milder form, where the blue cone is shifted; tritanopia is the stronger form, where the blue cone is absent and the blue-yellow axis collapses more completely.

Is blue-yellow color blindness more common in men or women?

About equal. The gene for the blue cone is on chromosome 7, not the X chromosome, so unlike red-green color blindness it is not far more common in men.

Can blue-yellow color blindness be acquired later in life?

Yes. Many tritan cases are acquired rather than inherited, from lens aging, glaucoma, diabetes, or certain medications. A new or one-sided blue-yellow change is a reason to see an eye-care professional.

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Color vision deficiency

Blue-Yellow Color Blindness

Blue-yellow color blindness, or tritan deficiency, involves the eye's blue (S) cone. It makes blue hard to separate from green and yellow from pink or violet. It is far rarer than red-green color blindness and affects men and women about equally because the gene is not on the X chromosome. The two forms are tritanomaly, the milder shifted-cone form, and tritanopia, the stronger form where the S-cone is absent.

Most color blindness is red-green; blue-yellow is the uncommon other branch. The S-cone handles short-wavelength ("blue") light, and when it is weak or missing the eye loses the contrast it uses along the blue-yellow axis. One catch: blue-cone signals are weak even in normal vision, so blue-yellow results are the hardest to judge on an uncalibrated screen.

The two forms of blue-yellow color blindness

Both involve the blue (S) cone. Prevalence figures are approximate and vary by population.

The two forms of blue-yellow (tritan) color blindness, the cone affected, severity, what they confuse, and how common they are
Form	Cone affected	Severity	What's confused	How common
Tritan (blue cone)
Tritanomaly	S (blue), shifted	Mild–moderate	Blue–green and yellow–pink	Very rare (<0.01%)
Tritanopia	S (blue), absent	Strong	Blue–green, purple–red, yellow–pink	Very rare (~1 in 10,000)

What colors does blue-yellow color blindness confuse?

The confusions run along the blue-yellow axis rather than the red-green one. Blue gets mixed with green, yellow with pink or light grey, and purple with red because purple contains blue and that blue side fades. A clear sky can look greenish, and yellows can drift toward a washed-out grey.

It does not turn the world grey, and it leaves most reds and greens intact. What goes is the separation between cool blues and warm yellows, and the violet end of the spectrum tends to lose its distinctiveness.

Tritanomaly vs tritanopia

Tritanomaly is the milder form: the S-cone is present but shifted, so the blue-yellow weakness is partial. Tritanopia is the stronger form, where the S-cone does not function and the blue-yellow axis collapses much more completely. Both sit on the blue-cone side and are far less common than any red-green type.

Is blue-yellow color blindness inherited or acquired?

Inherited tritan deficiency exists but is rare. Because the gene sits on chromosome 7 rather than the X chromosome, it shows up about equally in men and women — unlike red-green, which is far more common in men. Many blue-yellow cases are acquired rather than inherited: aging of the lens, glaucoma, diabetes, and some medications can shift color vision toward a blue-yellow loss.

That acquired pattern matters. A new or one-sided change in blue-yellow vision is a reason to see an eye-care professional, since it can be a sign of an eye condition rather than a lifelong trait.

How blue-yellow color blindness is tested

Screening uses pseudo-isochromatic plates and arrangement tests. The Farnsworth D-15 is useful here because a tritan deficiency produces a distinctive blue-yellow confusion axis when the caps are arranged. Specific tritan plates also exist, though they are less common than the red-green Ishihara plates.

Online testing is least reliable on this axis. Uncalibrated screens reproduce blues and violets poorly, so treat any on-screen blue-yellow result as a rough flag and confirm it with an eye-care professional, especially if the change came on recently.

Check your color vision

Blue-yellow is the hardest axis to judge on a screen, so treat an online result as a flag. The color blind test screens for a deficiency and estimates the type, and the Farnsworth D-15 shows a tritan confusion axis clearly.

Take the color blind test

See also the full types of color blindness and red-green color blindness.

Blue-yellow color blindness — frequently asked questions

What is blue-yellow color blindness?: It is tritan deficiency — a weak or missing blue (S) cone that makes blue hard to tell from green and yellow hard to tell from pink or violet. It is much rarer than red-green color blindness and affects men and women about equally.
What is the difference between tritanomaly and tritanopia?: Tritanomaly is the milder form, where the blue cone is shifted; tritanopia is the stronger form, where the blue cone is absent and the blue-yellow axis collapses more completely.
Is blue-yellow color blindness more common in men or women?: About equal. The gene for the blue cone is on chromosome 7, not the X chromosome, so unlike red-green color blindness it is not far more common in men.
Can blue-yellow color blindness be acquired later in life?: Yes. Many tritan cases are acquired rather than inherited, from lens aging, glaucoma, diabetes, or certain medications. A new or one-sided blue-yellow change is a reason to see an eye-care professional.

Sources

Last reviewed June 28, 2026. Informational only and regularly reviewed — not a substitute for advice from an eye-care professional.