Types of Color Blindness: A Complete Guide to Every Form of Color Vision Deficiency

Most people think color blindness means seeing the world in black and white. In reality, total color blindness is extraordinarily rare. The vast majority of color-blind people see a full range of colors — they just confuse specific pairs that look identical to them but obviously different to everyone else.

Which pairs they confuse depends entirely on which type of color blindness they have. A person with Protanopia (red-blind) confuses different colors than someone with Tritanopia (blue-blind). The tests that detect each type are different too — the standard Ishihara test only screens for red-green deficiency, not blue-yellow.

This guide explains every clinically recognized type of color vision deficiency: what causes it at the cellular level, how common it is, what the world looks like through that lens, and which test detects it. We will start with the classification system ophthalmologists use, then work through each type in detail.

How Normal Color Vision Works

The human retina contains two types of photoreceptor cells: rods (which detect light intensity and enable night vision) and cones (which detect color). There are three types of cones, each tuned to a different range of wavelengths:

When all three cone types are present and functional, the brain combines their signals to distinguish approximately one million color shades. Color blindness occurs when one or more cone types are absent (dichromacy), shifted in sensitivity (anomalous trichromacy), or completely nonfunctional (monochromacy).

Notice that the L-cone and M-cone genes both sit on the X chromosome. Because males have only one X chromosome (XY), a single defective copy causes color blindness. Females (XX) need both copies to be defective — which is why red-green color blindness affects 8% of males but only 0.5% of females (National Eye Institute ^[1]). The S-cone gene sits on chromosome 7 — an autosome — so blue-yellow color blindness affects both sexes equally. For a deeper dive into the inheritance patterns, see our guide on the genetics of color blindness.

Red-Green Color Blindness (Most Common)

Red-green color blindness encompasses four subtypes — two mild (anomalous trichromacy) and two severe (dichromacy). Together they account for roughly 99% of all inherited color blindness. All four are X-linked recessive, meaning they primarily affect males.

Deuteranomaly (Green-Weak) — The Most Common Type

The M-cones (green-sensitive) are present but their peak sensitivity is shifted toward longer (redder) wavelengths. This means greens, yellows, and reds all appear more similar than they should. Deuteranomaly is the single most common form of color blindness worldwide — about 1 in 20 men have it.

Many people with mild deuteranomaly go their entire lives without knowing. They may notice that autumn foliage looks less vivid, or that certain shades of green and orange are hard to tell apart, but the shifts are subtle enough to pass unnoticed in daily life.

Protanomaly (Red-Weak)

The L-cones (red-sensitive) are present but shifted toward shorter (greener) wavelengths. Reds appear duller and darker than normal, and orange, yellow, and green look more similar to each other. Unlike deuteranomaly, protanomaly causes a noticeable dimming of red colors. This is clinically important because red warning lights, brake lights, and red text on dark backgrounds may appear less conspicuous.

Deuteranopia (Green-Blind)

The M-cones are completely absent. The person has only two working cone types (L and S), so they see the world through a two-dimensional color space instead of three. The entire red-orange-yellow-green range collapses into varying shades of brownish-yellow. Blues and purples appear similar to each other.

Deuteranopia is the severe form of deuteranomaly. While deuteranomaly shifts colors slightly, deuteranopia eliminates an entire axis of color discrimination. A ripe red strawberry on a green bush looks like one uniform color to a deuteranope.

Protanopia (Red-Blind)

The L-cones are completely absent. Like deuteranopia, the person sees through only two cone types (M and S). Red-green discrimination is lost, but with an important additional effect: reds appear very dark, almost black. This is because the L-cones are normally the primary detector of red light — without them, red wavelengths produce almost no signal.

This brightness reduction for reds distinguishes protanopia from deuteranopia clinically. A protanope sees a red traffic light as a dim, dark dot rather than a bright signal. This has safety implications for driving with color blindness, particularly at night.

Blue-Yellow Color Blindness (Rare)

Blue-yellow color blindness affects the S-cones (blue-sensitive). Because the S-cone gene sits on chromosome 7 (an autosome, not a sex chromosome), blue-yellow deficiency is not sex-linked — it affects males and females equally. It is also much rarer than red-green types.

Tritanomaly (Blue-Weak)

The S-cones are present but their spectral sensitivity is shifted. Blues appear greener, and yellows appear lighter or pinkish. Tritanomaly is inherited as an autosomal dominant trait, meaning only one copy of the defective gene is needed — a different inheritance pattern from all other color vision deficiencies, which are recessive.

Tritanopia (Blue-Blind)

The S-cones are completely absent. The person sees through only L and M cones, losing discrimination along the blue-yellow axis. Blues and greens become confused, yellows may appear pinkish or light gray, and the sky may look greenish. Purple is often indistinguishable from a dark reddish-brown.

Tritanopia is more often acquired (from disease, medication, or aging) than inherited. Conditions that can cause acquired tritanopia include diabetic retinopathy, glaucoma, age-related macular degeneration, and exposure to certain industrial solvents (Cleveland Clinic ^[3]). Screen for this type with our blue-yellow color blind test.

Complete Color Blindness (Monochromacy)

Monochromacy is the only form where the term "color blind" is literally accurate — these individuals see no color at all, or only a trace of blue. Both forms are extremely rare and carry additional visual symptoms beyond color perception.

Rod Monochromacy (Achromatopsia)

All three cone types are nonfunctional. Vision relies entirely on rod cells, which detect only light intensity — not wavelength. The result is true grayscale vision. But the consequences go far beyond color:

• Photophobia — Extreme sensitivity to bright light. Rods saturate in normal daylight, causing pain and whiteout. Most achromats wear dark tinted or red-filtered glasses indoors.
• Nystagmus — Involuntary rapid eye movements, often present from birth.
• Reduced visual acuity — Typically 20/200 or worse (legally blind in many jurisdictions), because the fovea (center of sharpest vision) contains almost exclusively cones, and without functional cones the fovea is essentially blind.
• Hemeralopia — Better vision in dim light than bright light (the reverse of normal).

Blue Cone Monochromacy

Only the S-cones (blue-sensitive) function. Both L-cones and M-cones are absent or nonfunctional. The person retains a limited sense of blue but cannot distinguish reds, greens, yellows, or oranges. Like achromatopsia, blue cone monochromacy causes reduced visual acuity and some light sensitivity — though typically less severe than rod monochromacy. Because it is X-linked, it almost exclusively affects males.

Acquired vs. Inherited Color Blindness

Not all color blindness is genetic. Acquired color vision deficiency can develop at any age due to disease, medication, or environmental exposure. Key differences:

Acquired blue-yellow deficiency is particularly common in adults over 65. As the lens yellows with age, it absorbs more short-wavelength (blue) light, producing a gradual tritanomaly-like shift. An estimated 3% of the population over 65 have clinically measurable acquired color vision deficiency (Colour Blind Awareness ^[4]).

Prevalence: How Common Is Each Type?

The following table consolidates prevalence data from population studies. Rates vary by ethnicity — these figures represent global averages. Northern European populations tend to have slightly higher rates; sub-Saharan African and Indigenous Australian populations tend to have lower rates (Birch, 2012 ^[5]).

Which Color Blind Test Detects Which Type?

Not all color blind tests are equal. Each test targets different types and provides different levels of diagnostic detail:

If you suspect you have color blindness but are not sure which type, start with our free Ishihara color blind test for a quick red-green screening. For a more comprehensive assessment that covers all axes, the Farnsworth-Munsell 100 Hue test identifies the specific type and severity. For a definitive clinical diagnosis, ask your ophthalmologist for an anomaloscope examination.

The Bottom Line

Color blindness is not one condition — it is a family of at least eight distinct types, each caused by a different photoreceptor problem, producing different color confusions, and requiring different tests to detect. The overwhelming majority of color blind people (about 95%) have some form of red-green deficiency, and most of those have the mild green-weak form (deuteranomaly) that they may never even notice.

Knowing your specific type matters for practical reasons: it determines which color blind test will actually detect your condition, whether color-correcting glasses (EnChroma, Pilestone) are likely to help, and which daily situations need the most adaptation. If you suspect any form of color vision deficiency, taking an online screening test is a free, immediate first step — followed by a professional evaluation for a precise diagnosis.

Want to understand how color blindness is passed from parents to children? Read our guide on the genetics of color blindness. Concerned about a child? See early signs of color blindness in children. Wondering about career implications? Check jobs for colorblind people.