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.
The color of blood which remains after washing the garment does not render the prayer invalid. An-Nawawi said: “A color or smell which is difficult to be removed is ineffective.”
Al-Mardaawi a Hanbali scholar, said: “A color, smell or both of them which remain after washing are ineffective according to the sound opinion of the Hanbali School of Fiqh.”
Allaah Knows best.