It's often useful to use color to indicate different states of a user interface. The problem with this approach is that if color is the only thing that distinguishes between the different states, there will be some people who can't see the difference because they're color blind. A friend of mine who was color blind had trouble distinguishing between a red dot and a green dot in a user interface. We needed to add a separate indicator to make sure he could quickly identify the differences. It's something you need to consider when developing user interfaces.
Download