Bromo Cresol Green Indicator is recommended as a pH indicator in growth medium for microorganisms. Bromo Cresol green (BCG) is a dye of the triphenylmethane family (triarylmethane dyes). It becomes yellow at acidic pH level (pH 3.8) and Blue-green at from pH 5.4. It is used as a pH indicator and as a tracking dye for DNA agarose gel electrophoresis.