The most reliable way to determine color blindness is through a clinical screening test administered by an eye care professional, but there are also strong clues you can spot on your own. About 1 in 12 men and 1 in 200 women have some form of color vision deficiency, and many don’t realize it until they fail a routine screening or notice they consistently disagree with others about the color of everyday objects.
Signs You Might Notice on Your Own
Color blindness rarely means seeing in black and white. Most people with the condition see colors, just a narrower range of them. You might struggle to tell the difference between red and green traffic lights (relying on position instead), mix up colors when picking out clothing, or have trouble reading color-coded charts and graphs. Some people first notice the problem when they label a color incorrectly and someone corrects them.
In children, the signs can look different. A child might color a tree trunk purple or a sky green without realizing anything is off. The American Optometric Association notes that severe color vision deficiency can cause a child to be misidentified as learning disabled, because so many early learning materials rely on color coding. Most children can be reliably tested after age 5, and the AOA recommends screening as early as possible so parents and teachers can adapt.
The Ishihara Plate Test
The Ishihara test is the screening most people encounter first. It uses circular plates filled with colored dots that form a number or pattern. If your color vision is normal, you’ll read one number. If you have a red-green deficiency, you’ll either read a different number or see nothing at all. The standard concise edition has 14 red-green test plates plus a demonstration plate. Scoring 12 or more correct indicates normal color vision, while anything below 12 points to a deficiency. That cutoff has been shown to catch color vision problems with 97% sensitivity and 100% specificity, making it extremely reliable as a first-pass screen.
The test also includes diagnostic plates that help distinguish between the two main types of red-green deficiency. On these plates, people with protan defects (reduced red sensitivity) trace a different line or read a different number than people with deutan defects (reduced green sensitivity). The entire test takes only a few minutes and requires no special equipment beyond the printed plates and proper lighting.
Types of Color Vision Deficiency
Color vision depends on three types of cone cells in your retina, each tuned to a different part of the light spectrum: red, green, or blue. Color blindness happens when one type is missing entirely or shifted slightly in its sensitivity.
The mildest and most common form is called anomalous trichromacy. All three cone types are present, but one responds to a slightly different range of light than it should. Reduced green sensitivity (deuteranomaly) is by far the most common form of color blindness overall. Reduced red sensitivity (protanomaly) is less common, and reduced blue sensitivity (tritanomaly) is extremely rare.
More severe forms involve a complete absence of one cone type. Without functioning red cones, you can’t perceive red light at all. Without green cones, green light disappears. Without blue cones, blue drops out. Complete color blindness, where someone sees only in shades of gray, is a separate condition called achromatopsia and is very uncommon.
Clinical Tests for Precise Diagnosis
If a screening test flags a deficiency, your eye care provider may use more detailed tools to measure exactly what type you have and how severe it is.
Farnsworth-Munsell 100 Hue Test
This test asks you to arrange a series of colored caps in order by hue, like sorting a rainbow. Your score depends on how often you place a cap out of sequence and how far off it lands. The results map your specific areas of color confusion, showing precisely where on the color spectrum your vision breaks down. It’s particularly useful for tracking whether a deficiency is getting worse over time.
Anomaloscope
Considered the gold standard for diagnosing inherited red-green defects, the anomaloscope works by asking you to match two fields of light. One side shows a yellow reference light. The other shows a mixture of red and green that you can adjust. A person with normal color vision will only accept a very narrow mix as a match. Someone with a red-green deficiency will accept a much wider range, because the two colors look more similar to them. The width of that acceptable range directly reflects how severe the deficiency is. A person who matches every possible mixture is diagnosed as fully dichromatic (completely missing one cone type), while someone who matches a broader-than-normal but still limited range has a milder anomaly.
CAD Test
The Colour Assessment and Diagnosis test is a computer-based exam used in specialized settings like aviation. The FAA accepts it for pilot certification. It generates a numerical score for red-green and yellow-blue sensitivity. A red-green score below 1.7 is considered normal. Higher scores indicate a deficiency, with different passing thresholds depending on whether the defect is protan or deutan type. This test is particularly useful when someone needs to prove their color vision meets a specific professional standard.
Why Online Tests Have Limits
Plenty of websites offer free Ishihara-style screening tests, and they can be a reasonable starting point. But the results depend heavily on your screen. Monitor brightness, color calibration, display resolution, and even the lighting in your room all affect how colors appear. A study comparing online Ishihara plates to the standard printed handbook found the biggest discrepancies on the most subtle plates, likely because of differences in the spectral quality of screen light versus the standardized conditions the test was designed for.
If an online test suggests you have a deficiency, it’s worth confirming with a proper clinical screening. If an online test says you’re fine but you still struggle with colors in daily life, don’t assume the screen result is more accurate than your own experience.
Color Blindness That Develops Later in Life
Not all color vision deficiency is inherited. You can develop it from eye diseases like glaucoma or age-related macular degeneration, neurological conditions like Alzheimer’s or multiple sclerosis, certain medications (including some used for rheumatoid arthritis), and eye or brain injuries such as retinal detachment. Cataracts can also gradually dull your color perception as the lens of your eye becomes cloudier with age.
Acquired color vision loss is different from the inherited kind in a few important ways. It can affect one eye more than the other, it may involve blue-yellow confusion rather than the more common red-green type, and it can change over time as the underlying condition progresses or is treated. If your color perception shifts noticeably, that’s worth mentioning to your eye care provider, because it can sometimes be an early signal of a condition that hasn’t been diagnosed yet.
What Happens After a Diagnosis
There’s no cure for inherited color blindness, but knowing your specific type and severity makes a practical difference. You can adjust your environment: label clothing colors, use apps that identify colors through your phone’s camera, and request accommodations at school or work for color-coded materials. Some people find that specially tinted lenses enhance the contrast between colors they normally confuse, though these don’t restore normal color vision.
For children, an early diagnosis lets parents alert teachers before color-dependent assignments become a source of frustration. For adults, it can explain years of small misunderstandings and help with career planning in fields where color discrimination matters, like electrical work, graphic design, or aviation. The diagnosis itself is straightforward and painless. Most screenings take under ten minutes.