Color blindness — more accurately referred to as color vision deficiency or CVD — affects about 300 million people globally, per advocacy organization Colour Blind Awareness. It’s one of the most prevalent vision conditions, but CVD is occasionally overlooked in web accessibility discussions.
That’s partly due to some common misconceptions about color blindness. As is the case with many other disabilities, CVD doesn’t have a single set of symptoms, nor does it affect every person’s day-to-day life in the same way. Here’s a look at several of the most common myths.
Myth: Only males are color blind
About 95 percent of people with CVD are male, but about 1 in 200 females have some form of color blindness.
CVD is most typically caused by different genetic variations. Red-green color blindness, for instance, is caused by a recessive gene on the X chromosome. Men typically have one X and one Y chromosome, so if they inherit the recessive gene, they’ll develop red-green CVD.
When a person has two X chromosomes, however, the mutation must exist on both chromosomes in order for the condition to develop. Blue-yellow color vision develops from an autosomal dominant pattern, and it’s about as common among males and females.
In other words, anyone can be color blind — but people with XY chromosomes are much more likely to develop some form of color blindness.
Myth: Color blindness means a total inability to distinguish colors
Some people have monochromatic vision (achromatopsia, also called "total color blindness"), which means that they aren’t able to distinguish colors at all. Most individuals with monochromatic vision also have an increased sensitivity to light and other vision issues.
However, some physicians believe that achromatopsia shouldn’t be regarded as a division of color blindness, and the condition is much more rare than other forms of CVD; the National Institute of Health estimates that achromatopsia affects 1 in 30,000 people worldwide.
Myth: Color blindness means you can't see red or green
Red-green color blindness is the most common type of CVD, but it’s not the only variant, and the severity of the condition varies from person to person. Per the National Eye Institute of the NIH, there are two main types of color blindness, each of which is divided into subtypes: red-green (protanomaly, deuteranomaly, protanopia, and deuteranopia) and blue-yellow (tritanomaly or tritanopia).
People with protanopia or deuteranopia are unable to tell the difference between red and green at all, but people with other types of red-green color blindness only have trouble distinguishing between different shades of those colors. Possibly adding to the confusion, people with blue-yellow color blindness often have trouble distinguishing reds and greens as well.
Myth: Color blindness is always diagnosed at an early age
Color vision deficiencies aren’t always severe, and many people with CVD don’t receive a clinical diagnosis until adulthood (if they ever receive a diagnosis). It’s important to note that everyone sees color differently, and when color blindness is mild, people might not notice color deficiencies in their daily lives.
And while most color blindness is genetic, deficiencies can develop over time due to injuries or conditions like glaucoma. Some medications, including hydroxychloroquine, can also cause color blindness in adults.
Myth: Color blindness isn't challenging
While CVD doesn’t cause serious health issues, it can prevent people from taking certain occupations (for instance, pilots with significant color deficiencies can’t operate aircraft at night, per FAA regulations) and can present other challenges.
For instance, people with CVD might be less capable of navigating websites that rely heavily on color coding. Accessibility features can help; both iOS and Android have color accessibility settings that apply special filters to the phone screen to present visual content in a more intuitive way.
By planning for accessibility, web developers can improve the user experience for people with color blindness. This starts at the design level. Google Chrome includes accessibility tools for developers, including features that simulate color vision deficiencies, blurred vision, and other visual impairments. Developers can use these tools to prevent contrast issues from affecting site usability.
As always, the best approach is to prioritize accessibility early in web development. By following WCAG guidelines and paying close attention to the use of color, a developer can ensure that people with color blindness or other color perception variations aren’t left out — and that they’re able to experience the website in a natural and intuitive way.