When is purity from menstruation considered achieved if red blood continues for four days, then is followed by a brown discharge and a white discharge with a brown spot, or if there is dryness followed by a very small brown spot?

A woman recognizes ritual purity by one of two signs: dryness, indicated by the cotton coming out clean, with no trace of blood, yellowish discharge (ṣufra), or brownish discharge (kudra), or the white discharge (al-qaṣṣah al-bayḍā’). Whichever of these two signs is found first is sufficient to indicate purity. If she sees purity by one of its signs, she performs ghusl (ritual bath) and prays, and she should not be concerned about any yellowish or brownish discharge she sees after that, because it is not considered menstruation. However, any yellowish or brownish discharge seen continuously with blood is considered menstruation.