It wasn’t until my second year at university that I discovered I had a form of colour blindness.

I discovered this when my supervisor told me to click on the green folder on the screen. But I couldn’t see any green folders…

So, being the adept computing device user that I am, I naturally found myself staring at the colour blindness Wikipedia page. I ended up doing these “Ishihara tests” designed to test your blindness to colour. Sure enough, the tests showed I was actually colour blind — albeit mildly — and that I have the most common condition called ‘deutans’ (otherwise known as red-green colour blindness).

Number 74 in a circle made of coloured dots

Caption from Wikipedia: Example of an Ishihara colour test plate. With properly configured computer displays, people with normal vision should see the number “74”. Many people who are colour blind see it as “21”, and those with total colour blindness may not see any numbers.

Until this point, I had assumed that people with colour blindness don’t see any colours at all (monochromacy). That is, I thought people with colour blindness continuously saw the world as if it’s a showing of Casablanca.

So how does all this relate to learning and teaching?

This discovery helped explain why I’ve had trouble viewing some graphs. It was hard for me to distinguish between colours!

Given that a significant portion are affected by some form of colour blindness (around 8% of people with Northern European ancestry have deutans — mostly males), we can take some steps to make teaching material such as graphs and diagrams more legible.

100 figures, 8 in blue, 92 in black

Caption: Approximately 8% of people with Northern European ancestry have deutans — mostly males.

One easy way is to use a tool like Color Oracle (download the app), which simulates colour blindness conditions. Then you can assess legibility quite easily.

Some further tips include: (see figures 4 and 5 of this document for more inspiration):

Use different shapes and different kinds of lines

Apply different background patterns/textures appropriately-

Textures used in shapes or charts, allow for greater distinction between shapes.

2 line graphs, the left one more dull in colour

Avoid clashing colours

There are known colour combinations that are difficult for people with colour blindness to distinguish. Click on the link for more information.

Check if the material also makes sense in a black-and-white context, and that there is enough contrast

5 different shapes, all grey coloured

Annotate/label appropriately

5 different shapes labelled

Happy chart making!

Thanks to Fidel Fernando for his help with the charts!

Posted by Arun Neelakandan

One Comment

  1. Good one, Arun!


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