A film that instantly springs to mind when considering color as a communicative mean is "Kill Bill Volume 1". This film takes place in the present day in Quentin Tarantino's somewhat post-modern universe. The main character (who's name is not given in the first film, but is referred to as The Bride) was part of an elite assassin death-squad called the Deadly Viper Assassination Squad. After being impregnated by her boss and squad leader, Bill, she left, only to be attacked during her wedding. After a several year coma, she awakens to find that her child is not only alive, but also with Bill. In an action-filled revenge spree, The Bride systematically tracks down and eliminates members of the Deadly Viper squad.
Color is used throughout the film, namely the colors red and yellow. For instance, The Bride adorns herself with a bright yellow jumpsuit and drives a bright yellow car elegantly titled "The Pussywagon" (which currently resides in Tarantino's driveway). The gore in the film is exaggerated, with excessive bright red blood that dresses each scene The Bride visits. A scene in the movie, describing the upbringing of one of The Bride's ex-coworkers, is done in an anime-style cartoon. It uses dark and light colors to emphasize the story's emotions.
While the color in "Kill Bill Volume 1" is most definitely a thematic catalyst, a lack of color also plays a particularly important role in the film. Upon laying eyes on any of her nemeses, loud sirens start to play and the screen is saturated with a red tone. During the final gore-fest, the film is entirely black and white. Tarantino may have chose to do that to understate the violence and gore of the scene. Limbs fly and blood is spilled, but all in black and white. Later, The Bride returns to the scene of the massacre, but the scene is now in color. This way, the viewer sees the action during the colorless scene, but later sees the true mayhem when The Bride revisits the scene. This allows the viewer to get two perspectives of the scene, one in which the violence is present but some of the graphic elements are missing, and again, when the viewer can see the destruction caused by The Bride. The first perspective detaches the viewer (a bit) from the violence -- Tarantino does this to simulate the detachment that The Bride feels while killing/injuring dozens of people. When The Bride returns to the scene, she, along with the viewer, witnesses the mayhem caused by her actions. Color, and lack of color, are used to simulate, in the viewer, the emotions and mindset of The Bride.
Below is the Lucy Liu cartoon scene mentioned above. WARNING: Graphic/NSFW