A high concentration of anthocyanins gives the skin of an apple its distinctive red color. Apples have been bred for centuries, and this practice has allowed some types of apples to bear a bright red skin, while others are green, yellow or paler shades of red.
Most red apples develop their rich red color upon ripening and are typically green before they are fully mature. The amount of anthocyanin in any particular type of apple can be further affected by environmental, nutritional and orchard management factors. The color of the skin of an apple is one of the main differentiators between cultivars.