How accurate is an online color blind test?

Online screening tests can indicate possible color vision deficiencies but cannot replace a clinical diagnosis. Monitor calibration, ambient lighting, and screen quality all affect results. If this test flags a potential deficiency, schedule an appointment with an eye care professional for a proper evaluation using standardized Ishihara plates.

What is the difference between protan and deutan color blindness?

Protan deficiency affects red-sensitive cone cells, making reds appear darker and harder to distinguish from greens and browns. Deutan deficiency affects green-sensitive cone cells and is the most common type, causing difficulty distinguishing green from red and certain shades of brown. Both fall under the category of red-green color blindness.

Can color blindness be cured?

Most color vision deficiencies are genetic and cannot be cured. However, specially tinted glasses and contact lenses can enhance color distinction for some people. Acquired color blindness from medications, disease, or aging may improve if the underlying cause is treated.

Color Blind Test

Color vision deficiency, commonly called color blindness, affects roughly 8% of men and 0.5% of women worldwide. Most people who have it are born with it and never realize anything looks different to them. The condition happens when one or more types of cone cells in the retina respond to light wavelengths differently than expected, making certain color pairs difficult to tell apart. Red-green deficiency is by far the most common type, but blue-yellow deficiency also exists and is often overlooked.

I built this screening tool after learning that many people discover their color vision deficiency only when it causes a real problem at work or while driving. The test uses Ishihara-style dot plates rendered entirely in SVG. Each plate contains a number hidden within a pattern of colored circles. If your color vision is typical, you will see the number clearly. If you have a deficiency in a particular color range, the number will be difficult or impossible to distinguish from the background dots.

This test screens for three types of deficiency: protan (red-weak), deutan (green-weak), and tritan (blue-yellow). It takes about two minutes to complete all ten plates. Keep your screen at normal brightness in a well-lit room for the most reliable results.

Screening tool only. This test is not a clinical diagnosis. Monitor calibration, screen quality, and ambient lighting can all affect your results. If you receive anything other than a normal result, I recommend scheduling an appointment with an eye care professional for a proper evaluation using standardized testing equipment.

What number do you see?

Your Results

Remember. This is a screening tool, not a medical diagnosis. If any category shows a possible deficiency, visit an optometrist or ophthalmologist for a full color vision evaluation. They use controlled lighting and calibrated physical plates that provide far more reliable results than any screen-based test.

How Ishihara Plates Work

Dr. Shinobu Ishihara developed his color perception test in 1917 while working at the University of Tokyo. The original test uses 38 printed plates, each containing a circle of dots in varying sizes and colors. A number or path is embedded within the dot pattern using colors that people with normal color vision can easily distinguish from the surrounding dots. The specific color combinations are chosen so that a person with a particular type of color deficiency will see either no number, a different number, or only a faint trace.

The plates in this online version follow the same principle but are generated using SVG rather than printed ink. Each plate uses a circle packed with small dots in carefully chosen hue ranges. The background dots and the number dots are designed to differ primarily in hue while staying similar in lightness and saturation. This is the key mechanism: people with normal color vision distinguish hues easily, while people with a color deficiency rely more on lightness differences, which these plates intentionally minimize.

Types of Color Vision Deficiency

Red-green deficiency (protan and deutan)

This is the most common category, affecting about 6% of men. Protan deficiency involves the red-sensitive (L) cone cells, making reds appear darker and harder to separate from greens and browns. Deutan deficiency involves the green-sensitive (M) cone cells and causes a similar confusion between reds and greens but without the darkening effect. Both are X-linked recessive traits, which is why they appear far more frequently in men than in women.

Blue-yellow deficiency (tritan)

Tritan deficiency is much rarer, affecting fewer than 1 in 10,000 people. It involves the blue-sensitive (S) cone cells and makes it difficult to distinguish between blue and green, and between yellow and violet. Unlike red-green deficiency, tritan deficiency is not sex-linked and affects men and women at equal rates. It can also be acquired later in life through aging, certain medications, or eye disease.

When Color Vision Matters

Color vision plays a larger role in daily life than most people expect. Traffic lights, electrical wiring, cooking (judging whether meat is done), map reading, choosing clothing, and many workplace tasks all rely on accurate color perception. Some professions require formal color vision testing, including aviation, maritime navigation, electrical work, and certain medical roles. Knowing about a deficiency early lets you develop workarounds and avoid situations where misidentifying a color could cause real problems.