Friday, February 02, 2007

Testing for color blindness

A topic that I discuss in almost every workshop I do is how you need to be careful when using red and green because a certain percentage of the population has some degree of red-green color blindness. The medical studies suggest it is about 9-11% of Caucasian males and much lower in females and non-Caucasian males (I don’t know why and I am not sure the doctors know either).

There is a site I ran across recently that will help you see what someone with color blindness will see when they look at your slides. It is at . It allows you to upload a JPG or PNG graphic file and it will show you what people with the most common types of color blindness will see when they view your slide. To use it with PowerPoint, you must first save your slide or slides into the PNG or JPG format. To do so, click on File - Save As. In the Save as type drop down box at the bottom of the dialog box, scroll down until you find the PNG or JPG format. Then click the Save button and decide whether you want to save one slide or all slides if it asks you (usually one slide should be sufficient for this test).

Then you can upload the saved image file and use the tool to see what your slide will look like. It does show you what someone with yellow/blue color blindness will see but my research indicates that this type is so rare that I would not worry about it too much. Use this tool when you know someone with color blindness will be in your audience or when speaking to a large group where the chances are at least some of the people will be affected.


Blogger Daniel said...

Men have it more often because it's a sex link trait. So women have a second chance to cure the problem and this makes them less fragile than men.

By the way on presentations: Try not only to stick to colors but also use signs and patterns to support the message (e.g. thumb up for green).

1:16 PM  
Blogger Linda Adams said...

Another good way to see if it can be read by someone who is color blind is to simply print it on a black and white printer. If color is required for understanding of content or is hard to read, it'll start to become obvious in b/w where there is no color!

7:46 AM  

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