Sweet potatoes are a bright orange, starchy tuber that seem to gain recipe steam in the autumn and winter months. Sweet-tasting and full of nutrients, including vitamin A, fiber and antioxidants, sweet potatoes are a welcome addition to any dish. There also are purple sweet potatoes, of which many people are unaware. Anthocyanin lends the purple sweet potato its unusual violet hue. Purple sweet potatoes contain antioxidants with anti-inflammatory properties similar to red wine. After purchase, sweet potatoes should be stored in a dark, cool location.