How can a woman distinguish between a white discharge (al-Qassah al-Bayda') and a yellowish discharge (al-Sufrah), given that the white discharge may sometimes appear yellowish, and the secretions may be mixed? Should she fast and pray during these days? And does she become pure immediately upon the cessation of blood, or after the place dries, and what is the necessary duration for dryness to consider her pure?

The sign of purity (ṭuhr) is seeing a white discharge, free from yellowness (ṣufrah) and turbidity (kadrah). If you have doubts, you remain in the state of menstruation until you are certain of purity. The white discharge (al-qaṣṣah al-bayḍā’) is not considered purity until it is free from yellowness. If a woman performs ghusl while there is yellowness, it is more cautious to make up her prayers and fasting. The white discharge must be free from yellowness. It is not necessary for the area to be dry to determine purity; rather, the cessation of blood is sufficient. Dryness (jufūf) means that the cloth comes out dry, with no blood, yellowness, or turbidity on it. It is more cautious for a woman to perform ghusl whenever she sees purity. If yellowness appears after ghusl, then if it is within the period of her usual habit, it is considered menstruation. If it is outside the period of her usual habit, it is not considered menstruation.