How can the days of prayer and fasting be determined after menstruation, knowing that yellowness connected to menstruation is considered menstruation, and that dryness is followed by the discharge of transparent or yellowish fluids at certain times?

If a woman sees yellowness (صفرة) before her usual sign of purity, such as complete dryness or the white discharge (القصة البيضاء), it is considered part of menstruation and prohibits prayer and fasting, unless the duration of menstruation, including the yellowness, exceeds fifteen days. As for yellowness and turbidity (كدرة) after seeing the sign of purity, they are not considered anything, and do not prohibit prayer or fasting; rather, they only necessitate ablution (wudu').