CHROMagar Candida is a proprietary agar that contains undisclosed chromogenic substrates for metabolic enzymes that color growing yeast colonies and that enables certain species to be differentiated (16). HexNAcase-positive C. albicans and C. dubliniensis strains gave green or blue-green colonies on CHROMagar Candida, and these multiply subcultured isolates could not be reliably differentiated. Interestingly, C. albicans HexNAcase− mutant EOB4 grew as white (uncolored) colonies on CHROMagar Candida. Clinical C. albicans isolate I24, which could utilize GlcNAc but which produced detectable HexNAcase only after 48 h of incubation, grew as green colonies on CHROMagar Candida and was indistinguishable from C. albicans A72. I23 formed bluish colonies within the color range for C. albicans strains, whereas I7 formed deep blue colonies distinct from the colors of the colonies of the other C. albicans strains. The two strains of C. rugosa that gave very low levels of HexNAcase activity in the microtiter plate-based assay could be distinguished from C. albicans on CHROMagar Candida by a blue-purple colony color.