It is named for James Homer Wright, who devised the stain, a modification of the Romanowsky stain, in 1902. Because it distinguishes easily between blood cells, it became widely used for performing differential white blood cell counts, which are routinely ordered when infections are expected, and as part of an assessment of overall health.
There are related stains known as the buffered Wright stain, the Wright-Giemsa stain, and the buffered Wright-Giemsa stain, and specific instructions depend on the solutions being used, which may include Eosin Y, Azure B, and Methylene Blue (some commercial preparations combine solutions to simplify staining). The May-Grünwald stain, which produces a more intense coloration, also takes a longer time to perform.
White blood cells stained with Wright's stain: