ed Grapes - Seedless are small to medium in size and are round to slightly oblong in shape, growing in medium to large clusters. The hue of a Red seedless grape can vary widely depending on the variety and local growing conditions, but it usually ranges from a light red to a deep burgundy. The thin skin may also contain a dusty film, also known as a bloom, and this layer forms a natural waterproof barrier which prevents the delicate skin from cracking. The translucent flesh is juicy and is considered seedless, though a few small undetectable and undeveloped seeds may be present. Red seedless grapes are firm, crisp, and sweet with a mild, neutral flavor. Red seedless grapes contain significant amounts of vitamins A, C, and K, and contain flavonoids, such as resveratrol, which provide high antioxidant qualities that can help boost overall health.A half-cup serving of seedless red grapes supplies just 29 calories, making them a smart choice for weight-loss and weight-maintenance regimens. With 8 grams of carbs in a serving, red grapes make a low-glycemic snack for those following a diabetic diet or anyone limiting their daily carbs. A serving offers small amounts of several vitamins, most notably 5 percent of the vitamin C adult men require daily and 6 percent of what women need. Vitamin C is a powerful antioxidant that boosts immunity, which can in turn help ward off an assortment of illnesses -- from cancer to heart disease to macular degeneration, a condition of aging eyes.