Why color choice matters in your presentations

February 12, 2007

Tree of Life

There I was, happily browsin…err…researching for you, my patient readers, when I came across another gorgeous example of visualization, courtesy of GrrlScientist, which she got from Flickr. Now, as y’all know, I’m huge fan of using images to convey complex stuff, and so I skipped down to the key:

  • The bacteria …[are]… orange nodes.
  • The archaea … are represented by red nodes…
  • The eukarya … are represented by yellow nodes ..


It amazes me that folks, especially biologists, still seek to paint distinctions with orange, red, and green, given the rather well known, I mean Intro-Biology well-known, phenomenon known as red-green colorblindness. It afflicts about 10% of North American males (as it is carried on the X chromosome). You’ve probably seen the Isihara color tests with the little circle of dots that make those with rgcb feel dim.

When I teach this subject to my freshman undergrads, I use the nifty Colorblind Web Page Filter to show what a rather gaudy floral image from the OU web page

Normal color vision

looks like to a person with red green color blindness:

Red Green colorblind image

Note, when I was uploading these two images I had to be extra careful not to mix them up, as they look identical to me (and about 1 in 20 of your fellow readers). So, there are two takehome messages for this post:

  1. If you use orange/red/green to provide critical contrast in a visual presentation, you will lose some fraction of your audience. For the most common types of colorblindness consider using the primary spectra: blue, yellow, red. Or use patterns.
  2. Once those 5-10 people in an audience of 100 figure out that you, an educated person, forgot about them, your audience, they are likely to be peeved. Disgruntled. And there will also likely be another handful of folks that roll their eyes at your mistake.

Is it worth giving up on even a single member of your audience for something that is so easy to fix?