Red-Green Color Blindness

What colors do red-green color blind people confuse?

The trouble is with pairs that share a red or green component, not with every color. Common mix-ups include green and brown, red and brown, green and orange, blue and purple (purple loses its red side and reads as blue), and pink and grey. Pale versions and low-light scenes are hardest because there is less color signal to use.

It shows up in ordinary tasks: telling medium-rare from well-done meat, reading a red ballpoint on white paper, spotting a green status light, matching a navy sock to a black one, or picking out red berries in a bush. None of this means seeing in grey. It means two colors that look different to most people can land in the same place.

Protan vs deutan: what's the difference?

Both are red-green deficiencies, and they can look similar on a hidden-number plate, but they break in different directions. Deutan types (deuteranomaly, deuteranopia) involve the green M-cone and keep roughly normal brightness — reds and greens lose their separation. Protan types (protanomaly, protanopia) involve the red L-cone, which also carries much of our sense of brightness in red light, so protans see reds as noticeably darker and dimmer.

That brightness clue is the practical tell. A protan may miss a red LED that looks lit to everyone else, or read a red traffic light as much dimmer than the green. Sorting which family you fall in takes an arrangement test like the Farnsworth D-15, not a plate test alone.

Why is red-green color blindness more common in men?

The genes for the red and green cones sit on the X chromosome. Men have one X, so one altered copy is enough to cause a red-green deficiency. Women have two X chromosomes, so a working copy on the other one usually covers for it — which is why they are affected far less often (about 1 in 200) and are often carriers who pass it on without having it themselves.

That is why it tends to run in families and show up at birth rather than later. A boy's odds are highest when his mother carries the gene. Color vision can change later in life too, but that acquired kind comes from eye disease, diabetes, or medication, and more often hits blue-yellow than red-green.

Do color blind glasses help red-green color blindness?

Filter glasses are made for this axis. By cutting a slice of the spectrum where the red and green signals overlap, they can make those confusable colors look more separated and vivid for some people — usually mild-to-moderate cases, and strongest in bright daylight. They do not give normal color vision, do not let you pass a clinical test, and do little for strong cases or for blue-yellow deficiency.

If you are considering glasses, check your type and degree first. A protanope with a strong deficiency and a person with mild deuteranomaly will get very different results from the same lens.

What does a red green colorblind person see?

Someone who is red green colorblind sees a full, saturated world with one stretch of it compressed. Blues and yellows come through normally and often look vivid. What narrows is the range running from red through orange and yellow into green, which folds into a single family of warm tones instead of a sequence of distinct hues. Nothing looks grey, and nothing looks missing — the colours simply stop being separable from one another.

Ask someone red green colorblind to describe it and you usually get examples rather than adjectives, because there is no felt sense of absence. Strawberries hiding in the leaves. A green charging light that might be amber. Red pen on white paper that reads as dark grey. A heat map where the bad numbers and the good numbers look the same. The difficulty is always with a specific pair in a specific context, never with colour in general.

The one difference worth listening for is brightness. Deutans report reds as bright but not distinctly red; protans report deep reds as dark, dull, or almost black. If a person tells you a red LED looks unlit, that is a protan clue rather than a general red-green one.

You can see this for yourself: the free color blind filter simulates protan and deutan vision live through your camera or on a photo, and what do color blind people see walks through side-by-side examples type by type.

How red-green color blindness is identified

Screening — whether a deficiency is present — uses pseudo-isochromatic plates like the Ishihara test, where a number hides in colored dots that only normal red-green vision separates cleanly. To estimate which family it is (protan or deutan) and how strong it is, eye-care professionals use arrangement tests such as the Farnsworth D-15, and in clinics an anomaloscope.

An online screening is a useful first check and catches moderate-to-strong cases reliably. Read the type as an estimate: mild red and green are easy to mix up, and no uncalibrated screen replaces an exam with an eye-care professional.

Sources

• National Eye Institute (NEI) — Types of Color Blindness
• NHS — Colour vision deficiency (colour blindness)
• American Academy of Ophthalmology — What Is Color Blindness?
• Colour Blind Awareness — Types of colour blindness

Last reviewed August 9, 2026. Informational only and regularly reviewed — not a substitute for advice from an eye-care professional.