Red-Green Color Blind Test

Detect Protanopia (red blindness) and Deuteranopia (green blindness) with our specialized red-green color vision test.

Red-Green Color Blind Test

This test uses C-shaped Landolt rings to screen for red-green color blindness. Find the gap in the colored ring and click directly on it.

•Look at the colored circle and find the gap (opening)
•Click directly on the gap in the ring
•If you cannot see the gap, click "I Can't See"

Understanding Red-Green Color Blindness

Red-green color vision deficiency is the most prevalent form of color blindness, representing roughly 95% of all inherited cases. It occurs when the cone cells responsible for perceiving red or green wavelengths of light are either absent or function abnormally.

Globally, about 8% of males and 0.5% of females experience some degree of red-green deficiency. The condition is inherited through the X chromosome, which explains the significant gender disparity — males carry only one X chromosome, so a single affected gene results in color blindness.

Protan Deficiency

Caused by reduced sensitivity or absence of long-wavelength (L) cones. Protanopia means complete absence of red cones, while Protanomaly means reduced red sensitivity. Reds appear darker and may be confused with black, brown, or dark green.

Deutan Deficiency

Caused by reduced sensitivity or absence of medium-wavelength (M) cones. Deuteranopia means complete absence of green cones, while Deuteranomaly means reduced green sensitivity. Greens tend to blend with reds, yellows, and browns.

Protan vs Deutan color blindness comparison chart showing how red, green, orange, yellow and brown colors appear differently with each type of red-green deficiency

Prevalence Breakdown (Males)

~5%

Deuteranomaly

~1%

Deuteranopia

~1%

Protanomaly

~1%

Protanopia

How to Take the Test

1. Start the Test

Click "Start Test" above. You'll see a colored circle (Landolt C ring) with a gap on one side.

2. Find the Gap

Look at the ring carefully and click directly on the gap opening. If you cannot distinguish the ring from the background, click "I can't see the gap".

3. Get Your Results

After 14 rounds, you'll receive a detailed result indicating the severity of any red-green color vision deficiency detected.

How This Test Works

This test uses Landolt C rings — circles with a gap in one of eight directions. The ring is drawn in a color that people with red-green deficiency find difficult to distinguish from the surrounding background color. If you can see the ring clearly, you can locate and click on the gap; if you cannot distinguish it, the ring blends into the background.

The colors used for the ring and background are chosen along "confusion lines" in the CIE color space — pairs of colors that appear identical to people with a specific type of deficiency but are clearly different to those with normal vision. By varying these color pairs across 14 rounds, the test measures how well you can separate red-green hues.

The Landolt C Method

The Landolt C is a standard optotype used worldwide for visual acuity and color vision testing. Its simple shape — a ring with a single gap — provides a direction-based response that is language-independent and unambiguous. You simply click where you see the opening, making it accessible to users of any age or language background.

Why Gap Direction Matters

Unlike number-based tests where guessing is easy, the gap can appear in any of eight directions (up, down, left, right, and four diagonals). This makes random guessing unreliable (only 12.5% chance of a correct guess) and provides a more precise measurement of your ability to distinguish the ring from the background.

Scoring and Severity

Your score is based on how many of the 14 rounds you correctly identify the gap direction. Normal color vision typically achieves 90% or above. Scores between 70–89% suggest mild deficiency, 50–69% moderate deficiency, and below 50% indicates a strong red-green color vision deficiency.

Sources

National Eye Institute (NEI) — Comprehensive guide on color blindness types and genetic causes
American Academy of Ophthalmology (AAO) — Clinical information on red-green color vision deficiency
National Health Service (NHS) — Symptoms, causes, and management of colour vision deficiency
MedlinePlus Genetics — Genetic basis of red-green color blindness and X-linked inheritance
Colour Blind Awareness — Prevalence statistics and types of color vision deficiency

Frequently Asked Questions

Protanopia is caused by the absence of red-sensitive (L) cone cells, making reds appear very dark and easily confused with black or brown. Deuteranopia is caused by the absence of green-sensitive (M) cones, where greens blend into reds and yellows. Deuteranomaly (reduced green sensitivity) is the most common form, affecting about 5% of males.

Yes, but it is much rarer. Since the genes for red and green cone pigments are on the X chromosome, women need both X chromosomes to carry the affected gene. This occurs in about 0.5% of women, compared to 8% of men who only need one affected X chromosome.

There is currently no approved cure for inherited red-green color blindness. However, special tinted lenses and glasses can enhance color contrast for some individuals. Gene therapy research is ongoing and shows promise for future treatments.

This test provides a reliable screening indication, but results can be influenced by your display's color accuracy, brightness settings, and ambient lighting. For a definitive clinical diagnosis, visit an optometrist or ophthalmologist.

Beyond just red and green, affected individuals may confuse orange with green, brown with red, pink with gray, and purple with blue. The specific colors confused depend on whether the person has protan or deutan deficiency and how severe it is.

Yes. Based on how many of the 14 rounds you correctly identify the gap direction, the test indicates whether your deficiency is mild (70-89% correct), moderate (50-69%), or strong (below 50%).