Can you see anything in the pattern of this image?
If you choose colors for a software application, then make sure you print out a screen-shot of every screen on a regular black and white printer. If you can't understand something from looking at the printout, then you've used only colors to indicate something, and this will be a problem for up to 10% of your target audience.
The image above is part of a reverse colorblindness test. The image embedded in it is supposedly only visible to color blind people. I can see a circle very clearly but it would obviously be foolish to rely on color-typical people being able to see it.