Musnad Ahmad 1156:166

Abu Kamil Muzaffar ibn Mudrik narrated to us, he said: Zuhayr narrated to us, he said: Ali ibn Abd al-A’la narrated to us, from Abu Sahl, from the people of Basra, from Massah, from Umm Salamah, she said: "The woman experiencing postpartum bleeding during the time of the Messenger of Allah, peace and blessings of Allah be upon him, would sit [in seclusion] after her postpartum bleeding for forty days or forty nights." She said: "And we would apply *wars* (a yellow dye) to our faces because of the discoloration (melasma)."