What is the dye with which the Messenger, may Allah bless him and grant him peace, dyed his hair, and is it available today?

The Prophet, peace and blessings be upon him, frequently oiled his head and combed his beard. It is probable that he oiled it with olive oil, as he commanded its consumption and use as an anointment, saying: "Eat olive oil and anoint yourselves with it, for it comes from a blessed tree." No specific type of oil used by the Prophet, peace and blessings be upon him, has been definitively reported.