American History X- Filming

Im really interested in filming and the other day we had an assignment with finding an academy award winning film director, I chose Sydney Pollack and i analyzed The Talented Mr. Ripley which was a movie of his I really liked. Well this weekend I was watching American History X and I realized I was kind of analyzing it as I watched it (if you havent seen it I would cause its really good) and i realized some interesting filming techniques i never noticed before or that i noticed but never really thought of. For example when Edward Norton thinks back things turn black and white but somewhere while he's thinking back it just becomes color except its done so well that i dont even really notice the transaction till its already back to the present in the movie. I dont know i just thought it was really interesting how the movie was filmed and how that really added to the impact of it.