True black, uncoloured olives really do have many shades of colour: from brown to reddish, usually never uniform in colour, as nature creates. Black olives are picked when the fruit is fully ripe on the trees, which is why the colour is so different. Green olives are harvested before they are fully ripe, leaving them with a firmer flesh and a stronger flavour. The olive is initially always green and its colour is due to the presence of chlorophylls, but as ripening progresses the colour of the skin changes to pink-purple and at the end of ripening, due to the formation of anthocyanins, the colour turns black.
Olives are very versatile in cooking and, besides being exceptionally good and tasty, they are rich in antioxidant and anti-inflammatory nutrients and are a wonderful source of healthy gut bacteria.