On the basis of cell wall, bacteria can be divided in to Gram's positive or negative bacteria. Those stained by primary stain are positive while those which are not stained by primary stain are subjected to counterstain that is safranin and are known as Gram's negative bacteria, safranin gives pink or red color to Gram's negative bacteria and helps differentiating them from Gram positive bacteria which are have a violet or purple color due to primary stain of crystal violet.