What is the Ishihara color blindness test?

The Ishihara test is the most widely used color vision screening method, developed by Dr. Shinobu Ishihara in 1917. It uses pseudo-isochromatic plates — circles filled with colored dots of varying sizes and hues — where numbers or shapes are hidden within the pattern. People with normal color vision can see one number, while those with color vision deficiencies see a different number or none at all.

What are the types of color blindness?

The main types are: Protanopia/Protanomaly (red cone deficiency — difficulty perceiving red light), Deuteranopia/Deuteranomaly (green cone deficiency — the most common, affecting ~6% of males), Tritanopia/Tritanomaly (blue cone deficiency — very rare, ~0.01%), and Monochromacy (total color blindness, seeing only shades of gray — extremely rare, ~0.00003%). Red-green color blindness is the most common, inherited through the X chromosome.

How is color blindness inherited?

Red-green color blindness is an X-linked recessive trait, meaning the genes responsible are on the X chromosome. Males (XY) only need one affected X chromosome to be color blind, which is why ~8% of males but only ~0.5% of females have red-green deficiency. Females (XX) need both X chromosomes to be affected. A color-blind father passes the gene to all his daughters (who become carriers) but none of his sons. Blue-yellow color blindness follows a different, autosomal dominant pattern.

Color Blindness Test | Free Ishihara Color Vision Screening Online

Welcome to the Color Vision Test

This test uses pseudo-isochromatic plates — images made of colored dots with a number hidden inside. People with normal color vision see one number; people with color vision deficiency may see a different number or nothing at all.

🎯 12 Plates

A mix of demo plates, red-green screening, and type-specific detection plates.

⏱ ~3 Minutes

No time limit per plate. Take your time — accuracy matters more than speed.

🔒 100% Private

Everything runs locally in your browser. No data is ever sent or stored.

Medical Disclaimer: This online test is a screening tool for informational purposes only. It is not a medical diagnosis. Lighting conditions, screen calibration, and display quality can affect results. For a definitive diagnosis, consult an optometrist or ophthalmologist for a comprehensive color vision examination using standardized clinical equipment.

How to Take the Test

Four simple steps to screen your color vision.

Look at Each Plate

A circle of colored dots will appear on screen. A number is hidden within the pattern. View the plate in good lighting at a comfortable distance (approximately 60–75 cm / 24–30 inches from the screen).

Type What You See

Enter the number you can identify and click Submit. If you honestly cannot see any number, use the "I don't see a number" button. Don't guess — the test is most accurate when you report what you actually perceive.

Complete All 12 Plates

Work through each plate at your own pace — there is no timer. Different plates test different aspects of your color vision. The full set takes about 2–3 minutes.

Review Your Results

After the last plate, you'll receive a detailed assessment: your likely color vision status, which plates were missed, what type of deficiency (if any) the pattern suggests, and recommendations for next steps.

What is Color Blindness?

Color blindness — more accurately called color vision deficiency (CVD) — is the reduced ability to perceive differences between certain colors. It is most commonly an inherited condition caused by abnormalities in the cone cells of the retina, the light-sensitive layer at the back of the eye. Humans have three types of cone cells: L-cones (sensitive to long wavelengths — red), M-cones (medium — green), and S-cones (short — blue). Color vision deficiency occurs when one or more cone types are missing (anopia) or have altered spectral sensitivity (anomaly).

Approximately 1 in 12 men (8%) and 1 in 200 women (0.5%) worldwide have some form of color vision deficiency. The disparity exists because the genes encoding L and M cone opsins are located on the X chromosome — males have only one X chromosome, so a single altered copy is enough to cause deficiency, while females need both copies affected.

The 7 Types of Color Vision Deficiency

Type	Name	Cone Affected	Prevalence (Male)	What It Looks Like
Protanopia	Red blindness	L-cones missing	~1%	Red appears dark/brown; red-green confusion marked
Protanomaly	Red weakness	L-cones shifted	~1%	Red appears muted; mild red-green difficulty
Deuteranopia	Green blindness	M-cones missing	~1%	Green appears beige; red-green confusion marked
Deuteranomaly	Green weakness	M-cones shifted	~5%	Most common type; mild green perception loss
Tritanopia	Blue blindness	S-cones missing	~0.001%	Blue-yellow confusion; not sex-linked
Tritanomaly	Blue weakness	S-cones altered	~0.01%	Very rare; mild blue-yellow difficulty
Monochromacy	Total color blindness	2+ cones missing	~0.00001%	World appears in shades of gray

Red-green deficiencies (protan + deutan, all forms) account for approximately 99% of all color blindness cases. Blue-yellow (tritan) deficiency is extremely rare and affects males and females equally because the S-cone gene is on chromosome 7 (not sex-linked).

How Does the Ishihara Test Work?

This test is based on the Ishihara color vision test, developed by Dr. Shinobu Ishihara at the University of Tokyo in 1917. The Ishihara test uses pseudo-isochromatic plates — images composed of colored dots of varying sizes and hues arranged so that a number is visible to people with normal color vision but invisible (or a different number) to people with specific color deficiencies.

The key insight is that the dots are designed to differ only in chromaticity (color hue), not luminance (brightness). A person with normal trichromatic vision can distinguish the foreground number from the background dots by color. Someone with a cone deficiency, however, perceives these specific color pairs as identical, and the number blends into the background. This is why an Ishihara plate looks like a uniform field of random dots to a person with the relevant deficiency.

Each plate is carefully calibrated to test specific types of color vision deficiency by using color pairs that lie along confusion lines — pairs of colors that appear identical to a person with a given cone deficiency but distinct to a person with normal vision.

Careers Affected by Color Blindness

While most people with color vision deficiency live completely normal lives, certain professions require normal color vision due to safety or task-critical color discrimination:

Aviation: Commercial pilots, air traffic controllers, and many military aviation roles require passing an approved color vision test. Color signals are critical for runway lights, navigation displays, and cockpit instruments.
Electrical Work: Electricians must accurately identify color-coded wiring (red, green, blue, yellow, brown). Misidentification can be fatal.
Law Enforcement & Military: Some roles (particularly bomb disposal, forensics, and certain combat roles) require normal color vision for identifying colored indicators and signals.
Graphic Design & Digital Art: While not a formal barrier, color vision deficiency presents a practical challenge in professions requiring precise color matching, grading, and palette selection.
Railway & Maritime: Train drivers, signal operators, and merchant navy officers must correctly identify red, green, and yellow signal lights.
Chemistry & Lab Work: Many chemical tests rely on color-change indicators. Titration endpoints, pH strips, and certain assays depend on accurate color discrimination.

Living with Color Blindness

Color vision deficiency is not a disability — it is a difference in perception. Millions of people live full, successful lives with CVD. Coping strategies include labeling clothing, using smartphone apps that identify colors (such as Color Blind Pal, Seeing AI, or built-in accessibility tools), relying on brightness and position cues rather than color alone, and being upfront with colleagues about visual limitations. Specialized glasses (such as EnChroma) can enhance color contrast for some people with red-green deficiency, though they do not "cure" color blindness — they work by filtering specific wavelengths at the boundary between confused colors. Famous individuals with color blindness include Facebook founder Mark Zuckerberg (red-green), actor Keanu Reeves, former US President Bill Clinton, and artist Neil Harbisson (who has complete achromatopsia and uses an antenna implanted in his skull that converts color into sound).

Frequently Asked Questions

Common questions about color blindness and online testing.

How do I know if I'm color blind?

Many people with mild color vision deficiency reach adulthood without realizing it. Common signs include: difficulty distinguishing red from green (traffic lights, colored text on backgrounds, ripe vs unripe fruit), colors appearing "muddy" or washed out, frequent disagreements about color names, and struggling to read colored text on colored backgrounds. If you suspect color blindness, take this screening test and then confirm with an eye care professional.

What are the 7 types of color blindness?

The 7 recognized types of color vision deficiency: Protanopia (L-cones missing, red-blind), Protanomaly (L-cones shifted, red-weak), Deuteranopia (M-cones missing, green-blind), Deuteranomaly (M-cones shifted, green-weak), Tritanopia (S-cones missing, blue-blind), Tritanomaly (S-cones altered, blue-weak), and Monochromacy (total color blindness). Red-green types (protan + deutan) account for 99% of cases.

Can color blindness be cured?

There is currently no cure for inherited color vision deficiency — it is a genetic condition present from birth and typically stable throughout life. Gene therapy research is ongoing (animal studies have successfully restored cone function in squirrel monkeys), but this is not yet available for humans. Specialized glasses and contact lenses can enhance color discrimination for some users but do not restore normal color vision. Acquired color vision loss (from cataracts, certain medications, or retinal disease) may sometimes be treated by addressing the underlying cause.

How accurate is an online color blindness test?

Online tests are screening tools, not diagnostic instruments. A well-designed online Ishihara test can detect moderate-to-severe red-green deficiency with approximately 85–95% sensitivity compared to clinical testing. However, it may miss mild cases, and it cannot distinguish between protan and deutan types with the same precision as an anomaloscope. For a definitive diagnosis, consult an eye care professional.

Do color blindness glasses really work?

Color blindness glasses (such as EnChroma) use optical notch filters to block specific wavelengths where L and M cone sensitivities overlap most. For people with anomalous trichromacy, these glasses can increase perceived color contrast between red and green. However, they do not "cure" color blindness, do not restore normal vision, don't work for dichromats, and don't enable passing clinical color vision tests. They are an assistive tool, not a medical treatment. Experiences vary widely.