Phenol Red Color Chart. Phenol red is a ph indicator which turns yellow below a ph of 6.8 and fuchsia above a ph of 7.4. Reagents marked with an * are considered to be potential health hazards.
Phenol red fermentation medium contains peptone, phenol red (a ph indicator) and the carbohydrate to be tested. Most commonly, phenol red is an indicator dye, used as an acid ph indicator with a transition point of 7.5 (acid side to yellow / alkaline side to red) biologists use phenol red in cell cultures. Above ph 8.2, phenol red turns a bright pink color.