Should a woman pray if her menstrual period continues longer than usual, or if the color of her blood changes?

If a woman sees purity by one of its two signs (dryness or white discharge) and then sees yellowish or brownish discharge outside her usual period, it is not considered menstruation.

However, if the yellowish or brownish discharge is continuous with blood and exceeds fifteen days, then it is irregular bleeding (istihada). In this case, the woman experiencing istihada must refer to her previous habitual period and consider that as menstruation, and anything beyond it as istihada.

If the woman recovers from istihada and sees purity for fifteen days (which is the minimum period of purity), then any blood she sees thereafter is considered menstruation, as long as it does not exceed fifteen days (which is the maximum period of menstruation).