The next time you walk down the produce aisle, let color be your guide: the more intense the pigment of a fruit or vegetable, the richer it is in health-promoting compounds. Blueberries, blackberries, and strawberries pack the highest nutritional wallop, says Dr. Luke Howard, professor of food science. They owe their vivid colors to generous portions of cancer-fighting pigments. As a bonus, blackberries and strawberries also contain vitamin C. Deep green vegetables like spinach and broccoli also score high in the nutrition game, but even pale vegetables like onions contain pigments that protect against heart disease. They've also been shown to lower cholesterol and maintain a healthy immune system. Here again though, color counts: red and yellow onions have more nutrients than white ones. The same holds true for tomatoes: they get their scarlet color from lycopene, which may protect against prostate cancer, and the redder they are, the more lycopene they have.