Bernhard Jenny in Switzerland wrote Color Oracle, a nifty and free utility for simulating color blindness that no self-respecting programmer, UX practitioner, or web site designer should be without. It runs on Mac, Windows, and Linux.
I downloaded and tried the Mac version. It works well. When you run it, a small icon installs itself on the menu bar. To see your screen the way that a color blind person would, click on the icon and select one of three types of color blindness. Here is an example of before (left) and after:
The simulation is not continuous: once you’re seeing your screen in the eyes of a color blind person (usually male), pressing any key will return you to normal mode. But Color Oracle lets you assign a keyboard shortcut to each color blindness type, making it easy to simulate quickly. It’s a great way to get a “reality check”, in the words of Nathaniel Kelso, who helped with ideas and testing.
My first brush with what one can do for color blind persons was a 2007 post by Greg Raiz. Greg described how Apple was using red and green circles (same shape) to illustrate which stores had iPhone availability, and how they later switched to using different shapes (snapshot used with permission):
For a company that cares deeply about user experience, one would expect Apple to provide a similar utility to its developers, preferably with continuous simulation instead of snapshots. But until then, Color Oracle is a great addition to our toolbox.