G6PD and G6PD deficiency: Fairbanks and Beutler designed a quick, cheap, and simple method of detecting G6PD deficiency based on the reduction of a tetrazolium dye, which turns purple in the reduced state.53 Later, Fairbanks and a colleague described a method of staining individual erythrocytes for G6PD, based on the reduction of a tetrazolium salt to a chromogenic formazan dye.