Phlegm and mucus are technically one and the same: Phlegm is mucus that is created in your respiratory system, especially your chest, while fighting an infection—a byproduct of inflammation in your airway., Phlegm can be a variety of colors, including clear or white, green or yellow, red or pink, brown, or gray or black. When phlegm is expelled from your airway by coughing, it’s called sputum.