Microbiology Corynebacterium diphtheria produce black or grey colonies on the following agar A Mac-conkey agar B Potassium tellurite agar C Thayer main medium D Tinsdale agar 💡 Explanation Corynebacterium diphtheria produce black or grey colonies on the following agar ✓ Correct Answer: B. Potassium tellurite agar