What is the interpretation of the presence of white and black flags on mosque minarets on Friday?

Raising white or black flags over mosques on Fridays or other days of the week is not from the Sunnah, and it is considered an innovation (bid'ah) in religion, based on the Prophet's (peace and blessings be upon him) saying: "Whoever introduces into this matter of ours that which is not from it, it is rejected." There is no evidence indicating that the Prophet or his Companions did so.