Are olives dyed to make them black?

Answer

No. No dye is needed for olives to turn black. An olive cannot be eaten as it comes off the branch; during the processing methods applied in table-olive production, phenolic compounds naturally present in the olive oxidise and the colour darkens to black. The black colour is therefore the result of a natural chemical change during production. An olive's colour also varies with the time of harvest, the olive variety and the processing method used.