Perception Test - Color Vision
Color Blindness Test
12 Ishihara-style plates generated programmatically. Each plate hides a number in a field of colored dots. Enter what you see - Or tap "None" if you see no number. This is a screening tool, not a clinical diagnosis.
Color Vision Screening
You will see 12 plates. For each, enter the number you see, or click "None". Take the test in good lighting. Remove any tinted glasses or contacts.
This is a screening tool only. A formal diagnosis requires examination by an optometrist or ophthalmologist.
What number do you see?
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How color vision works
Normal human color vision is trichromatic - It relies on three types of cone photoreceptors in the retina, each sensitive to different wavelengths of light. S-cones peak at ~420nm (short/blue), M-cones at ~530nm (medium/green), and L-cones at ~560nm (long/red). The brain combines signals from these three channels through opponent-process encoding: a red-green channel, a blue-yellow channel, and a light-dark channel. The peripheral retina, which underlies peripheral vision, relies on rod photoreceptors rather than cones and is unaffected by color blindness.
Color perception emerges from the ratios of cone responses, not their absolute activation levels - Which is why colors look roughly constant under different lighting conditions (color constancy). Deficiencies in one or more cone types alter how the brain encodes these ratios, making certain color pairs indistinguishable. This also explains why color blindness tests work by encoding numbers in hue contrast rather than lightness contrast - A person with normal trichromatic vision easily reads the number, while someone with a specific deficiency cannot distinguish the figure from its background.
Types of color blindness
| Type | Defect | Colors confused | Prevalence (M) | Severity |
|---|---|---|---|---|
| Protanopia | L-cones absent | Red/green | 1% | Severe |
| Protanomaly | L-cones shifted | Red/orange | 1% | Mild–mod |
| Deuteranopia | M-cones absent | Red/green | 1.2% | Severe |
| Deuteranomaly | M-cones shifted | Green/yellow | 5% | Mild |
| Tritanopia | S-cones absent | Blue/yellow | <0.1% | Severe |
| Achromatopsia | All cones absent | All colors | <0.01% | Complete |
The Ishihara test
Dr. Shinobu Ishihara of the Imperial University of Tokyo introduced his pseudoisochromatic plate test in 1917, initially to screen Japanese army recruits. Over a century later, it remains the most widely used color vision test worldwide - Included in military entrance screenings, aviation medicals, and routine pediatric vision assessments in most countries.
Each Ishihara plate consists of a circular field of dots varying in color, size, and lightness. A number is embedded in dots of one hue against a background of dots in a confusable hue. Because the dots also vary in lightness and size, individuals cannot use brightness cues to identify the number - Only chromatic contrast works. The 38-plate standard edition includes demonstration plates (visible to everyone), screening plates (missed by color-deficient individuals), and diagnostic plates that differentiate specific deficiency types. The version in this test is programmatically generated to approximate the chromatic contrast of the standard plates and serves as a preliminary screening only. Because color rendering varies between displays, device choice can influence screen-based results - The same hardware effects documented in our mobile vs desktop reaction time comparison.
Who is affected? Genetics and prevalence
The most common forms of color blindness - Red-green deficiencies caused by mutations in the OPN1LW (L-cone) and OPN1MW (M-cone) genes - Are X-linked recessive traits. Because males have only one X chromosome, a single defective copy produces color blindness. Females have two X chromosomes, so both must carry the mutation - Making female color blindness approximately 16 times less common than male. An estimated 8% of males and 0.5% of females of Northern European ancestry have some form of red-green color deficiency.
| Population group | Prevalence (males) | Prevalence (females) |
|---|---|---|
| Northern European | 8% | 0.4% |
| East Asian | 5% | 0.3% |
| Sub-Saharan African | 3% | 0.2% |
| South Asian | 6.5% | 0.3% |
Living with color blindness
For most people, color blindness is a mild inconvenience rather than a disability. Common adaptations include relying on position cues (traffic lights are always red-top, green-bottom), choosing careers that do not require color discrimination, and using digital accessibility tools. Browser extensions like Chrome's Color Enhancer and apps like Colorblindness Simulator help both those with color blindness and designers who want to create accessible content.
EnChroma glasses use a notch filter to enhance chromatic contrast for people with red-green deficiencies. While they do not restore normal trichromatic vision, they can meaningfully improve color discrimination for individuals with anomalous trichromacy (protanomaly, deuteranomaly). They are less effective for dichromats (protanopia, deuteranopia) and do not help with blue-yellow or total color blindness. If you scored poorly on this screening, consider discussing a formal evaluation with an optometrist. Caring for your vision is one part of overall cognitive wellbeing - see our evidence-based guide to brain health.
When to see an eye doctor
Congenital color blindness (present from birth) is stable throughout life and does not worsen or cause other vision problems. However, acquired color vision deficiency - Color blindness that develops in adulthood - Can be a sign of underlying conditions including glaucoma, macular degeneration, diabetic retinopathy, multiple sclerosis, or toxic reactions to medications such as hydroxychloroquine, ethambutol, or digoxin. If your color vision has changed noticeably in adulthood, this warrants prompt optometric evaluation.
Occupations with color vision standards - Commercial aviation, electrical work, law enforcement, and certain military roles - Require formal testing with calibrated Ishihara plates, Farnsworth D-15, or Nagel anomaloscope, not online screeners. This test can indicate whether further testing is warranted but cannot serve as a formal occupational screening. Always work with a qualified clinician for those determinations. For other vision-related cognitive measures, explore the Peripheral Vision test and the Anti-Saccade test.
Color Vision Facts
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