All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
As long as this bleeding follows the menstrual bleeding without an interval, and the total duration of the bleeding is within15 days ,then it is considered menstruation, even if the color of the blood is different from that of the first days of the menstrual bleeding.
Allaah Knows best.