What is purpose of Congo red stain in capsule stain?

Congo red stain is used in capsule staining to visualize bacterial capsules, which are often not easily seen with standard staining techniques. It binds to the polysaccharide components of the capsule, providing a contrast against the background and the cells themselves. This allows for clear observation of the capsule's presence and size, aiding in the identification of certain bacterial species and their virulence factors. The stain typically appears as a red or pink halo surrounding the bacterial cells.