polychrome methylene blue

pol·y·chrome meth·yl·ene blue

an alkaline solution of methylene blue that undergoes progressive oxidative demethylation with aging (ripening) to produce a mixture of methylene blue, azures, and methylene violet.

polychrome methylene blue

the preferred stain for a smear when the presence of anthrax bacilli is suspected. A positive result is a McFadyean reaction of a purple capsule around a blue bacillus.