In the case of green and black olives, it is the same plant, it is only picked at different moments of ripening, which causes a difference in color.
The crop begins to grow in early summer, with green berries harvested in autumn from September and black around January. It’s worth clarifying here quickly that there really isn’t such a thing as black olives in nature. It’s purple, pink, grayish, dark brown (these are ripe ones that are harvested late) - the soot black available in stores is mostly painted with sulfate, which is why it has such a distinctive metallic aftertaste (the ones available at Buono! aren’t like that :))
Although they grow on the same tree, due to different treatment procedures, the berries will have completely different contents. There is much more salt in the green and more oil in the darker shades. The oil content of the berry is at its peak at the time of purification; the best olive oils are therefore made from purple olives, without any other added substances, only by pressing. The resulting olive oil is called extra virgin. Their energy content also varies: 15 grams of green olives contain 20 calories, while the same amount of black contains 25 calories.