Muslin is most typically an unbleached white cloth, produced from corded cotton yarn. Contrast muslins gives two different contrast colors because of the dying process.
You can have various options with the help of contrast muslin. The one side of the backdrop has denim texture and other side has blue, gives you versatality in your photography. The muslins are finished on all four sides.
Muslin is the most common backdrop material used by photographers for formal portrait backgrounds. You can reverse the muslin to get another set of color and contrast.