As tomatoes are ripe, they become red due to the presence of lycopene, a phytochemical (a biologically active compound produced by plants). Immature tomatoes have a high concentration of chlorophyll, another phytochemical that gives them their green color. The fruits ripen as the seeds within grow, through a series of chemical and physical changes that make them soft, flavorful, and (typically) red.
The colour change occurs as the chlorophyll breaks down and lycopene is produced, which signals to animals, including humans, that the fruit is ready to eat. Tomato seeds may survive passage through an animal’s digestive track, therefore the plant’s attractive red color is part of its seed-dispersal strategy.
