Display states

Just starting to get into Display States. When I have a single part, I have no problem changing the color of the part using Display States, but in an assembly, I am having trouble changing the color of one particular part using Display States. If I change the part to red in one display state, then try to change that part to blue in another display state, it changes to blue but when i go back to the red display state, the part is now blue. Obviously I am missing something here