Muslin is most typically an unbleached white cloth, produced from corded cotton yarn. And wash muslins is a cloth that is dyed in different colors.
This dark brownish khaki wash muslin will give a blend of single color muslin.
Muslins help in masking the background sets and helps to establish the mood or feel of different scenes. There are various colors of wash muslin but each one has variation of single color.
Wash muslin is the most common backdrop material used by photographers for formal portrait backgrounds.