Jackie's classic style consisted mostly of black and white clothing. It was her favorite look, and she was photographed wearing only black and white many times. She preferred white on the bottom (trousers or an A-line skirt) and black on the top, stating the other way around gives too much of a "waiter look."
This style is easy to imitate since it's so simple and gives you a complete outfit. Start with a pair of white, beltless jeans, and wear a black turtleneck pulled down over your hips. Add a three-strand pearl necklace or a headscarf, and you'll be an instant Jackie look-alike!