To style a black cardigan, start by layering it over a neutral-colored top, such as a white tee or a gray turtleneck. For a classic look, pair it with dark-wash jeans and ankle boots. Accessorize with a statement necklace or scarf. For a more casual look, wear it with leggings and sneakers. Add a pop of color with a brightly colored bag or shoes. To dress it up, wear it over a silk blouse or dress and add heels and jewelry.