Red or pink phlegm can be a more serious warning sign. Red or pink indicates that there is bleeding in the respiratory tract or lungs. Heavy coughing can cause bleeding by breaking the blood vessels in the lungs, leading to red phlegm. However, more serious conditions can also cause red or pink phlegm.

When should I be worried about mucus?

According to Dr. Bryson, mucus is typically not a symptom to worry about if it's your only symptom. “Worrisome signs are mucus accompanied by fevers, chills and night sweats, especially if you also experience weight loss, nasal obstruction or intermittent nose bleeds for more than two weeks,” he says.

What color mucus is good?

Clear. Thin and clear mucus is normal and healthy. White. Thicker white mucus goes along with feelings of congestion and may be a sign that an infection is starting.