Friday, March 13, 2009

An example of "Christmas Camouflage" graphics

In a previous post on February 10, 2009 I discussed “Christmas Camouflage” graphics. About 5% of your audience (basically 10% of the men) are color blind and can’t distinguish red from green. These are the folks who will show up for St. Patrick’s Day dressed in a red shirt and green trousers.

I just saw a post from January 8, 2009 on Jeromy Timmer’s Improvement in Practice blog about “What to put in your slides in ’09 (Part 2).” He talked about using a tool called Kuler to create a palette from an image. If you run his example with five colors through the Vischeck tool (which lets you see what a color blind person would) then you will see those five colors become just four, as shown above, because the blue shades at left and center merge. Would you have guessed that would happen?

We all have blind spots like this, and sometimes need to use one tool to check results from another. I have been using PowerPoint and choosing colors without much thought. Until I saw a post about Vischeck I had not considered that red-green color blindness could be an issue in presentation graphics. However, I should have known better based on my previous experience.

About thirty years ago I finished a hitch as a medic in the Air Force Reserve. One weekend a month my duties sometimes included doing vision tests, one of which was for color blindness. It involved flipping though a book of Ishihara plates containing numbers formed from colored dots and asking the subject to read the numbers.

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