One of the movies that I've seen that really shows interesting things in color is the movie The Graduate. Throughout the movie, the director uses color changes to show the main characters transition and advancement through out the film. In the opening scene, linked here, we see the character surrounded by white while the titles are shown in black showing a contrast between the reality and the backdrop of the film itself as the film progresses (without giving too much away) the choice in Dustin Hoffman's wardrobe becomes progressively darker, showing a change from the pure person that he was in the beginning. In addition to colors growing darker it also corresponds to the soundtrack in the background as often times the "Sounds of Silence" is used as a way of showing that things are escalating or at the end, when the main character is again in white (showing he is "pure" once again) and the song is played in a more uplifting fashion.
I look forward to your comments and thanks for reading!