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, Red onions are sometimes used as treatments for colds, diarrhea, intestinal parasites, gallstones, Red onions are available throughout the year.