When you cough
out the phlegm in the colour green or black it suggest your body is trying to expell the tars or resins built up from smoking
so try to avoid smoking to be on the safer side consult pulmologist for further evaluation and to prevent further complications due to smoking. Learn yoga
to improve the lung capacity and for the good blood circulation to the lungs. Add garlic in your diet regularly which acts as a natural expectant.
Hope this answers your query.