All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
It seems that the milk that comes out of the udder tainted with blood is pure and that there is no harm in using it. Scholars said that if the milk of the edible (halaal) animal comes out of the udder looking like blood, it is pure as long as the characteristics of milk remain in it. So this ruling applies to the milk tainted with blood with greater reason. They also held that such milk is pure as long as it has not transformed into blood or pus. Al-Khadeem said, "The milk that has been tainted in the udder is pure unless it has changed into blood or pus." [Sharh Al-Kafaaf]
Allah knows best.