How does olive oil turn your hair black?

The main reason hair turns gray or white is a lack of the proteins that provide the pigment for the hair. Heated olive oil applied to the hair may make it slightly darker, but its main effect is to moisturize dry hair.

The olive oil does not turn your hair black; it just helps it to grow silky and shiny. The extract shikakai (made from Acacia pods) will darken your hair and improve growth.