Is it permissible for a man to have intercourse with his wife if she saw a dried spot of blood before intercourse, then saw light bleeding during intercourse?

If intercourse occurs during menstruation, the husband must repent, and he must offer expiation by donating a Dinar or half a Dinar, because there is a narration to that effect, and because intercourse during menstruation is prohibited by the text of the Quran and Sunnah and the consensus of the Ummah. As for intercourse after the cessation of menstruation but before ghusl, it is prohibited according to most scholars, based on Allah’s saying: (And do not approach them until they are purified. But when they have purified themselves, then come to them from where Allah has ordained for you). Ibn Abbas interpreted "when they have purified themselves" as meaning performing ghusl. If the wife was compliant, she must repent; if she was coerced, there is no sin upon her.