Is the dark brown or red blood that came out two days after the IUD insertion, and hours after intercourse, following the cessation of menstruation, considered menstrual blood that prevents prayer, fasting, and intercourse?

If a woman sees the sign of purity, then any discharge thereafter is not considered menstruation, based on the statement of Umm Atiyyah (may Allah be pleased with her): "We did not consider any brownish or yellowish discharge after purity as anything." However, if blood returns for a full day and night, to the extent that it soils a cotton pad, it could be either a continuation of the initial menstruation, which prohibits prayer, fasting, and intercourse, or irregular bleeding (istihada), which does not prohibit any of these, depending on the detailed legal ruling.