How can one differentiate between yellowish discharge (ṣufra) and vaginal moisture (ruṭūbāt al-farj) connected to menstruation? Is everything with a yellowish tinge considered ṣufra, even if it is white with a slight inclination to yellow? What is the ruling on fasting and prayer in this situation?

There is no harm in the confusion between yellowness and vaginal discharge. The matter does not go beyond two situations:

Firstly: If the yellowish discharge appears before menstruation, or after it, immediately following the period, or during it and before purification: All of this is considered menstrual blood, and vaginal discharge has no ruling here.

Secondly: If the woman has purified herself, indicated by the clear white discharge or dryness: - Whatever discharge appears thereafter, if it is pure white and has no foul odor, then it is among the pure vaginal discharges that invalidate ablution. - If it tends towards yellowness visible to the naked eye, then it is an impure fluid that must be avoided and washed off, and it invalidates ablution. It is not considered menstrual blood because the period has ended. The distinction relies on the visible color; normal vaginal discharge is white, whereas the impure yellowish discharge has a clear yellow color. The odor of vaginal discharge may be foul due to infections, and it is recommended to consult a doctor in case of yellowish discharge after purification.