Is it permissible to place small, colored stickers inside the Mushaf to mark similar verses, in order to facilitate memorization for female Quran students?

There is no harm in placing small adhesive papers in the Mushaf (copy of the Qur'an) to mark similar verses, because there is nothing in Islamic law that prohibits it, especially since the intention behind them is to identify similar passages and they are not permanent. Furthermore, they are not considered written words that mix with the Qur'an, nor do they represent a humiliation of the Mushaf. There may even be a need for them.