Presenting to the colour blind

ishihara 24 by :nike

As part of my job I provide technical training to groups of software engineers. I relish this aspect of my job as it allows me to improve my public speaking and travel around the world for free. Unfortunately the training materials I am provided with are very poor quality. Most of the slides were written before I joined the company and are an excellent example of how not to use PowerPoint. Most of the slides are a dense set of monochrome bullet points. When diagrams are used they are invariably a set of boxes using the default PowerPoint colour scheme.

I have pointed out that we could be providing better visual aids if the diagrams made better use of colour. Selecting a colour to represent a certain topic or concept, and then using it consistently throughout the slide deck could provide fast visual cues that could be assimilated much faster than plain text.

A few weeks ago I found out why my pleas have been falling on deaf ears. Two of the contributors to the course are colour blind. This fact emerged after a this diagram was presented in a seminar:

This image is very difficult for colour blind people to interpret

Frankly, this diagram is horrible. Even without colour blindness the text begins to fade into the background when viewed from far away. The colour scheme adds an extra layer of difficulty for people with protanopia, an inability to distinguish between red and green. My colour blind colleague had difficulty making any sense of it.

An estimated eight percent of white males (the most affected group) in the USA have some form of colour blindness. This is a significant percentage which should be considered when designing visual aids.

Some suggestions about designing more accessible visual aids are made on the wikipedia article on colour blindness. It suggests avoiding colour keys and not relying on colour alone to present information. However there is no one size fits all solution.

A good rule of thumb would be to print your slides on a black and white laser printer. This will show up where you are relying on colour to make a point and where conflicting colours blend into each other. Problems can be fixed with clear labeling or replaced with textures. Along with making the slides more accessible to colour blind people, this exercise would make your black and white hand-outs will be more accessible to everyone.

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