What is the correct time to end menstruation and perform ghusl if transparent discharge, tending to dark reddish or brownish, continues for days after the bleeding stops? And is ghusl required again if black discharge appears after the first ghusl?

There are two signs of purity from menstruation: complete dryness of the area, so that no trace of blood remains, or the appearance of the white discharge (al-Qassah al-Bayda'). As long as one of these two signs has not appeared, the woman is menstruating and avoids what a menstruating woman avoids. The brownish or yellowish discharge connected to menstruation has the same ruling as menstruation. If a woman sees purity by one of the two signs, and then blood, brownish, or yellowish discharge appears, it is not considered menstruation. If the dark or yellowish blood continues uninterruptedly with what preceded it and does not exceed fifteen days, then it is menstruation. If it exceeds fifteen days, the woman considers the excess as istihadah (irregular bleeding) and makes up for the prayers and fasting she missed, and she returns to her usual cycle. However, if the blood stops and the area becomes completely dry, the woman is pure, and the return of dark or yellowish blood after her usual days does not affect her.