Many people believe green or yellow mucus signals a bacterial infection that requires antibiotics, but research shows phlegm color is an unreliable guide. The color comes from immune cells and is seen in plenty of viral infections that resolve on their own with rest, fluids, and time. Taking antibiotics when they are not needed will not speed recovery and contributes to antibiotic resistance.
What matters more is how unwell you are and how long symptoms last. See a doctor if you have a high fever that persists, increasing breathlessness, chest pain, you are coughing up blood, or you are not improving after about a week to ten days. People with asthma, COPD, heart problems, or a weak immune system should seek advice sooner.
Only a clinician or prescriber should decide if antibiotics such as amoxicillin are appropriate. A pharmacist can help manage symptoms in the meantime. Informational only.