Is it permissible to pray, fast, and engage in intercourse after ritual purity from menstruation if light bleeding occurs during intercourse, and do the spouses bear sin for that?

If a woman is certain of complete purity (tahara), then any blood spots that appear thereafter are not considered menstruation. She must wash her private parts, clean her clothes, and perform ablution for prayer. Her ruling is like that of pure women: she can fast, pray, and intercourse with her is permissible. A woman must not rush to perform ghusl (ritual bath) until she is certain of purity, which is indicated by one of two signs: seeing the white discharge (al-qassah al-bayda'), or complete dryness (al-jufūf al-tām).