Is the light-colored bloody spot that appears a day or two after the cessation of menstruation considered menstruation, and does intercourse after performing ghusl from menstruation, followed by the appearance of this spot, necessitate a sin?

The blood that returns on the fifth or sixth day is considered menstrual blood, because any blood a woman sees at a time when it is possible for it to be menstruation is considered menstruation. As for the purity preceding the return of the blood, it is a valid state of purity, and one must promptly perform ghusl (ritual bathing), prayer, and fasting after seeing purity, and it is permissible for the husband to have intercourse with his wife. If the blood returns again, one must refrain from prayer until it stops, then perform ghusl and prayer, as long as this occurs within the menstrual period. Therefore, there is no sin in the intercourse that occurred during the purity that intervened in the menstrual cycle.