Red onions, sometimes called purple onions, are cultivars of the onion with purplish red skin and white flesh tinged with red. These onions tend to be medium to large in size and have a mild to sweet flavor. They are often consumed raw, grilled or lightly cooked with other foods, or added as color to salads. They tend to lose their redness when cooked. Red onions are available throughout the year. The red color comes from anthocyanidins such as cyanidin. Red onions are high in flavonoids. They can be stored 3 to 4 months at room temperature.