in a particular scene by the colors being used. for example, if a bright, happy character dressed in yellow is suddenly thrown into a dark black scene, we as an audience might assume something bad is about to happen.
in a more complex way, color is also used to show character growth by having the character associated with certain colors at the beginning of the film and then slowly moving them through a series of colors at each developmental point in the movie, until they are finished growing and expanding. in the movie, the last emperor, the main character starts off surrounded by reds because he associates everything with this color, 