Red grapes are actually healthier than green grapes because they have a higher flavonoid content and are therefore richer in antioxidants than green grapes. The flavonoids cluster in the darker skin of the red grape.
Red grapes contain quercetin, a flavonoid that has anti-inflammatory and antihistamine properties and helps the immune system fight allergies. They also contain resveratrol, a flavonoid with similarities to synthetic estrogen that may be able to help ease the symptoms of menopause. The catechins, proanthocyanidins and stilbenes in red grapes may also have a preventative effect against breast cancer. Both red and green grapes contain high amounts of manganese, which strengthens bones and connective tissues.