Testing for colourblindess

Overview

It is estimated that 1 in 10 men have some form of colour blindness. This issue also effects women, but on a lower scale — around 0.5%. To maintain an inclusive design which is accessible to as many people as possible, it is important to carefully choose how to use colours. This applies to any situation. However, in this scenario, we are focusing on web and/or software applications.

Types of colourblindess

In brief, there are three types of colour blindess:

• Deuteranope: insensitivity to green
• Protanope: insensitivity to red
• Tritanope: insensitivity to blue.

The protans and deutans cover 99% of the colour blind population.

Points to consider

When testing an application, it is important to review the colours being used. This can be done using various free online or downloadable tools. By selecting the colours being used within your application, these tools will tell you if the contrast is sufficient. In some cases they will provide you with examples of how it might look.

It is also important to check whether colour alone is used to display meaning. For example, a red text error message may not be enough for a colour blind person to notice it is an error. In this case you may want to consider alternatives such as making the error text bold or making it a larger size.

Colour blindness resources and tools

• VisCheck
• Colour Contrast Analyzer
• Web accessibility toolbar