If the olive pit is black, does it mean dye was used?

Answer

No. A dark olive pit is related to the ripeness of the fruit. As the olive ripens on the tree, the phenolic compounds it naturally contains move inward starting from the skin; as ripening progresses these natural compounds can reach the pit and darken its colour. A black pit therefore points to the natural ripening process, not to the use of dye. The overall colour of an olive can also vary with ripeness, variety and the processing method applied. The separate question of why olive flesh turns black is covered in another entry.