Are the black spots that appeared on clothes, due to leaving them in a place with ritual impurity (najasah), considered ritually impure (najis), and must they be removed by washing, even if the clothes were washed with water and soap and the spots did not disappear?

The original state of clothes is purity, and they do not become impure by being placed in an impure location unless their impurity is certain. If the impurity of a spot is certain, then only the impure area must be purified. If it is difficult to remove the color of the impurity, its remaining after washing the spot does not cause harm. Washing the blood is sufficient, even if its trace does not disappear.