When thinking about color in film the first thing that came to my mind was the use of the color red in American Beauty. American beauty is itself a type of rose with a vibrant red color that recurs throughout the film in different ways. The most obvious is the picture that I used as my media example of the character Angela Hayes in a sea of the red flowers as Lester Burnham fantasizes about her. I have read a few interpretations of this scene and the color, and the one that makes most sense to me is it being a symbol for Lester's lost youth and the sexuality and counter-culture life that he grew up in and was a product of before he became a spineless working stiff. As he fantasizes about her and the vibrant red, he is flooded with the youth that he once had and his motivation in the film is to get with Angela and in a way get his 'mojo' back.
The roses also recur when Lester fantasizes about Angela during the halftime show of the high school basketball game where she is a cheerleader. Lester becomes mesmerized by Angela's vitality and the film portrays himself as the only one sitting in the stands as Angela seductively dances for him and eventually roses flow out of her shirt as Lester almost voyeuristically watches.
The roses also creep into lester's home as his wife Carolyn meticulously prunes the roses. In Carolyn's case, she has no interest in re-visiting her youth but rather moving on; she wants to be the housewife that sells real estate as a career and wants a home life. One could say that her manicuring the red roses represents her want of leaving her youth in the past and perfecting the life that she desperately wants to live (and fails at).
All in all, there is a symbolism to the vibrant red that is used in American Beauty; for Lester Burnham it is his desire for youth and his lust for Angela and for Carolyn it is her desire to be the perfect housewife.