In fruit & veg different colours are caused by varying plant pigments that add nutritive value; each colour family has specific health benefits. The deeper the colouring, the more effective the nutrient.
Red colouring comes from the plant pigments, either lycopene or anthocyanins. Lycopene, which colours, among others, tomatoes and watermelon, is most touted for its cancer-fighting properties — especially prostate cancer in men. Anthocyanins provide antioxidants, which protect cells and also guard against heart damage, and are particularly effective against colon cancer. They are found in many red berries.
Orange- and yellow-toned fruits and veggies — encompassing most citrus fruits, many varieties of squash, peaches, carrots, and corn, among others — are coloured by the plant pigments carotenoids. Orange-toned fruits and veggies contain beta-carotene, which is converted to vitamin A and is particularly helpful in maintaining visual health and healthy mucous membranes. Yellow-toned examples, including most citrus fruits, contain less vitamin A but more vitamin C — another antioxidant — and the B vitamin folate.
Green fruits and veggies are coloured by chlorophyll, the same pigment that colours most inedible leaves. Dark greens like spinach, green peppers and cucumbers, contain lutein, which is important for vision health. Leafier greens tend to contain folate; more yellow-toned green veggies also contain the carotenoids present in yellow vegetables. Green veggies also contain the cancer-fighting phytochemicals sulforaphane and insoles.