What are the main types of color blindness?

There are three families. Protan types affect the red cones, deutan types affect the green cones, and tritan types affect the blue cones. Each comes in an anomalous form, where the cone works but is shifted, and a complete form, where that cone type is missing entirely. Deuteranomaly is the most common by a wide margin.

What is the most common type of color blindness?

Deuteranomaly, a green-weak deficiency, affecting roughly 6 percent of men. It is a partial deficiency rather than a complete absence of green cones, which is why many people who have it never realize until they take a test.

Why does color blindness affect men more than women?

The genes for red and green cone pigments sit on the X chromosome. Men have one X, so a single faulty copy causes the deficiency. Women have two X chromosomes and would need the fault on both, which is far less likely. Blue-yellow deficiency is not X-linked, so it affects both sexes equally.

Can color blindness be cured?

No. Genetic color vision deficiency cannot be cured because the cone cells themselves are absent or shifted. Special filter glasses can increase the perceived separation between confusable colors for some people, but they do not restore normal color vision.

What is the difference between anomaly and anopia?

The suffix -anomaly means the cone type is present but its sensitivity is shifted, giving reduced discrimination. The suffix -anopia means that cone type is entirely absent. So deuteranomaly is green-weak while deuteranopia is green-blind, and the anomalous forms are much more common.

Types of Color Blindness and How to Test for Them

What causes color blindness?

Color blindness (color vision deficiency) occurs when one or more types of cone cells in your retina are absent or function differently. Most cases are genetic and affect about 8% of men and 0.5% of women of Northern European descent.

The three main types

Protanopia and Protanomaly (Red-weak): Reduced sensitivity to red light. Reds appear darker and can be confused with greens, browns, and blacks. About 1% of men have protanopia (complete red cone absence) and 1% have protanomaly (partial red cone function).

Deuteranopia and Deuteranomaly (Green-weak): Reduced sensitivity to green light. Greens can be confused with reds and yellows. This is the most common form, affecting about 6% of men. Deuteranomaly (partial) is far more common than deuteranopia (complete).

Tritanopia and Tritanomaly (Blue-weak): Reduced sensitivity to blue light. Blues can be confused with greens, and yellows with purples. This is rare, affecting less than 0.01% of the population. Uniquely, it affects men and women equally because it is not linked to the X chromosome.

How to get tested

Our Color Blindness Test provides a quick screening using patterns inspired by Ishihara plates. While this cannot replace a clinical examination, it can indicate whether professional testing is warranted.

For a definitive diagnosis, see an optometrist or ophthalmologist who can perform an Ishihara test (printed plates), an anomaloscope test, or a Farnsworth D-15 test.

Living with color blindness

Color blindness is not a disability for most daily activities. Most people with color vision deficiency adapt and function normally. However, certain professions (airline pilot, electrician, some medical fields) require normal color vision.

Modern technology helps: most operating systems and smartphones include color blindness accessibility filters that shift colors to be more distinguishable. Many apps and games now include colorblind-friendly modes.

How each type sees the world

Protan (red-weak): Red appears noticeably darker than it does to normal vision, not just different in hue. A red traffic light can look almost black, and red text on a dark background can disappear entirely. Reds, browns, oranges and greens compress toward each other.

Deutan (green-weak): Brightness perception stays close to normal, but greens and reds sit much closer together. Green and brown become hard to separate, as do blue and purple. Because brightness is unaffected, deutan deficiency is easy to live with unnoticed for years.

Tritan (blue-weak): Blue and green become confusable, and yellow can appear pink or grey. Unlike the red-green types this is usually acquired rather than inherited, often from aging, eye disease, or certain medications.

Testing methods beyond Ishihara plates

Ishihara plates are the familiar screening test, but they only reliably detect red-green deficiency. Clinicians use several others:

Farnsworth D-15: arranging colored caps in order, which reveals the axis of the deficiency.

Anomaloscope: the reference standard, where you match a mixed red-green light to a yellow reference. It distinguishes type and severity precisely.

Cambridge Color Test: a computerized test that adapts difficulty and works for tritan deficiency too.

A screening test on a web page cannot replace any of these, because screen calibration alone can shift results.

Designing for color vision deficiency

If you build interfaces, the practical rules are simple. Never rely on color alone to carry meaning: pair it with shape, an icon, or a text label. Avoid red on green and green on brown combinations. Keep contrast ratios high, since luminance difference survives every type of deficiency. Test your palette by simulating protanopia and deuteranopia, which together cover the overwhelming majority of affected users.