What is the ruling on the light yellow discharge that continues after menstruation and is only seen by inserting a cotton swab, and must the missed prayers be made up because of it? And what is the ruling on a married woman inserting a cotton swab to verify purity? And are the brown and red discharges that precede menstruation and are seen after an IUD insertion considered menstruation?

A woman identifies purity from menstruation by one of two signs: dryness (inserting a cotton swab that comes out clean), or the white discharge (a white fluid that appears after menstruation). Yellowish and brownish discharges are considered menstruation if they are connected to blood or occur during the period of menstruation. They are not considered menstruation after seeing purity. If a woman sees blood after seeing purity from menstruation, it is considered menstruation if it occurs at a time suitable for menstruation (for example, if the total days of both blood flows and the purity between them do not exceed 15 days, or if 15 days or more separate it from the previous blood). Blood that appears before 15 days and is not connected to the previous menstrual period is considered istiḥāḍah (irregular bleeding). So, if a woman sees blood in the last two days of Ramadan, it is menstruation, and she must refrain from prayer and fasting and make up those two days, unless it is istiḥāḍah blood, in which case she is not required to make up the fast.