differential staining differential staining differential staining is a staining process which uses more than one chemical stain. using multiple stains can better differentiate between different microorganisms or structures/cellular components of a single organism. differential staining is used to detect abnormalities in the proportion of different white blood cells in the blood. the process or results are called a wbc differential. this test is useful because many diseases alter the proportion of certain white blood cells. by analyzing these differences in combination with a clinical exam and other lab tests, medical professionals can diagnose disease. one commonly recognizable use of differential staining is the gram stain. gram staining uses two dyes: crystal violet and fuchsin or safranin (the counterstain) to differentiate between gram-positive bacteria (large peptidoglycan layer on outer surface of cell) and gram-negative bacteria. acid-fast stains are also differential stains.