Living with colour vision deficiency (CVD) can mean missing out on important content, but it doesn’t have to be that way. Learn how to improve access to your content for people living with colour-vision deficiency.
Colour blindness is really colour vision deficiency
Colour blindness is more accurately described as colour vision deficiency (CVD). This is because very few people are unable to see any colour at all. Most people living with CVD have some colour vision, but have difficulty distinguishing between certain combinations of colours. While specific kinds of CVD are more common in certain groups, CVD can affect anyone regardless of their age, sex or ethnicity. There are different types of CVD, which we’ll cover below.
The most common forms of colour vision deficiency relate to red-green CVD, which causes difficulty distinguishing between red and green:
- Deuteranomaly makes green look more red
- Protanomaly makes red look more green and less bright
- Protanopia and deuteranopia both make it impossible to distinguish between red and green
Source: National Eye Institute
Blue-yellow CVD is rarer but affects a wider range of colours:
- Tritanomaly makes it hard to distinguish between blue/green and yellow/red combinations
- Tritanopia makes it impossible to distinguish between the following colour sets: blue/green, purple/red and yellow/pink. Colours also look less bright.
Source: National Eye Institute
Achromatopsia or monochromacy is very rare but often has a greater impact than other forms of CVD. People living with Achromatopsia will likely see the world in shades of grey or blue. They also often have a severe intolerance to light (Hemeralopia) and low vision.
What software can and can’t do for people living with CVD
People living with milder forms of CVD can sometimes improve their vision by using software colour filters, such as those provided in the Windows Colour filters and MacOS X Colour Filters. These filters should not, however be relied on to fix problems with existing content as their effectiveness can vary. They also provide no solution for people who can’t distinguish between some colours at all.
How CVD affects the appearance of content
Consider the following column graph that shows quarterly shipments for a frozen berry company:
On first glance this graph may seem fairly easy to read, but it’s really only completely accessible to people with full colour vision. Now take a look at the same graph with a blue-yellow CVD simulation applied:
If you have full colour vision you’ll see that it’s very hard to spot the difference between the two left hand columns; the two right hand columns are equally difficult to tell apart. Now take a look at a monochrome version of the same graph:
In this version it’s very hard to see the difference between the first and third columns from the left. It’s impossible to see the difference between second and the fourth columns from the left.
Design solutions to the rescue
There are some simple design solutions that you can use to make your content more CVD-friendly.
Using patterns on graphs, charts and diagrams can make colour irrelevant and is the most reliable way of making content CVD-friendly. Adding patterns makes it much easier to tell the difference between columns:
Patterns also make it easy for anyone viewing content in monochrome:
Use a CVD friendly colour scheme
Check if your colour scheme is CVD friendly using the Adobe Accessible colour palette generator. You’ll be able to see if the colour scheme is likely to cause issues for people living with CVD and find alternative, CVD friendly colours if required.
Labels for data series
Use labels for data series so users have more than one way to differentiate parts of your content from each other.
Long text descriptions
Provide visible long text descriptions of non-text content where possible, as some users with achromatopsia may also have low vision. Visible long text descriptions are more useful than alt-text in when working with complex visual content; they can be accessed by everyone and can help users living with a range of disabilities.
You can learn more about making your content accessible in our accessibility collection on LX Resources.