Stain bacteria contrasting coloursAnswer:Differential stains work by using a series of dyes and sometimes additional chemicals, to stain bacteria contrasting colours based on structural difference between bacterial cells. The Gram stain, acid-fast stain and endosperm stain each reveal distinct information about the bacteria tested.The Gram stain, developed by Christian Gram in 1800’s, was the first differential staining technique in use and is still an important tool for distinguishing between two main types of bacteria—Gram-positive and Gram-negative.