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Developing reports for colour-blind people

July 2nd, 2009
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According to Wikipedia 8% of all males and 0.4% of all females in Australia are colour-blind to some degree. The percentages are slightly different in the USA – 7% for males and 0.4% for females. It is estimated that these would be similar to other countries in the world, which means that a very high percentage of people may have difficulties distinguishing colours. Therefore, a significantly large part of our potential report users may not be able to interpret some of our graphs and charts correctly (There would be around 400 colour-blind males and 20 colour-blind females in an organisation which employs 10000 people).

In example, the following chart is quite nice and simple but can be useless to colour-blind people:

chart-colour

versus:

chart-grey

Similarly, this table is somewhat confusing if we remove the colours:

table-colour

versus:

table-grey

We have to be very careful with design of KPIs and dashboards in general:

kpi-colour

versus:

kpi-grey

As we can clearly see from the above examples, not being able to clearly distinguish colours makes our poorly designed charts and tables confusing.

We should always keep in mind the following considerations when designing and implementing our most-common report items to ensure that they can be used by everyone in our client organisation:

  • KPI indicators must be different in shape rather than just colour
  • Line charts should utilise markers with different shapes
  • Bar graphs should include a marker on the top of each bar
  • Avoid colour-coded pie-charts – they can be extremely difficult to read for a person with even the slightest colour-blindness condition
  • Avoid colour-coding tables – either backgrounds or text colours are usually unacceptable

Other more general suggestions:

  • Shapes are much more important than colours
  • Greyscale and shades of the same colour are acceptable, as a colour-blind person can distinguish between those

Of course, even after all our efforts to create reports readable by everyone, we may miss some detail. The best way to ensure that we have done a good job is to test. There are two good and easy ways to do that:

  1. Printing – print the report in black and white and see if all information is well presented
  2. Changing display to greyscale – Windows lets us choose how many colours we want to display on our screen. Choosing greyscale and then playing with our report is possibly the best way to ensure that colour-blind people can use our reports.

It is fairly simple and easy to always apply these design principles when creating reports. I have found that most organisations are quite happy to include minor tweaks to their dashboards and reports when they understand how important they could be for some of their employees. Furthermore, it helps to promote accessibility to technology regardless of minor disabilities and gender.

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