People tend to use red, green, and blue on white backgrounds, because those are simple colours that are dark enough to stand out. But that can be a problem for deuteranopes.
Andy Baio has a great post about reading graphics with his “broke-ass eyes,” as he put it. There are some great tips there.
Did you know that Photoshop has a colour-blind simulator? I didn’t.
Even better, Andy points to Vischeck, an online colorblind simulator. I ran several posters that I had previously critiqued through the simulation. Luckily, most of them held up pretty well. Here are a couple of examples (click to enlarge).
The overall effect is much more monotone, but the poster is still quite legible overall.
This one has a more serious issue. The figure in the upper right corner might not interpreted properly by someone who is red-green colour blind.
If you want to use red and green to distinguish data on a graph, make sure that the data is distinguished by some other characteristic than just colour. Don’t use red and green circles; use red circles and green triangles. Don’t use red and and green lines; use a red solid line and a green dashed line.
And you can’t go wrong with good ol’ black text and lines on a white background.
I found that once I was reminded of how common colour blindness is, I became sensitized to it, and started noticing potential problems. A little planning can go a long way in making your posters legible for colour blind people.