This is a good use of color to a visualization with a lot of data. Jonathan Harris developed an interactive system that collects feelings data on people's feelings on the web.
"The interface to this data is a self-organizing particle system, where each particle represents a single feeling posted by a single individual. The particles’ properties – color, size, shape, opacity – indicate the nature of the feeling inside, and any particle can be clicked to reveal the full sentence or photograph it contains. The particles careen wildly around the screen until asked to self-organize along any number of axes, expressing various pictures of human emotion. We Feel Fine paints these pictures in six formal movements titled: Madness, Murmurs, Montage, Mobs, Metrics, and Mounds."