The director used black and white and colors to show the stark contrast between the background and the focus to draw the movie-goers gaze. The bright red of a dame's lips or the deep green of her eyes. The movie was reminiscent of the old Dick Tracy comics. I kept expecting to see a <POW> or <BAM> to show up.
I give Sin City a D- because of the large number of famous cast members. When Lady Gaga looks normal in a movie compared to everyone else, run! Save your money for school supplies!