Thanks for the great post. I first became sensitive to this issue years ago when I discovered that one of my QA testers was red/green colorblind and couldn’t tell that the icons in the server dashboard actually meant something. The icons were traffic lights with different “lights” turned on for different states. I ended up redesigning the icons to include shape clues in addition to color cues and my tester was amazed at how much functionality he hadn’t even been aware of before.