I have coughed up green and now brownish-grey phlegm and have felt flu like symptoms for over a week, is it possibly pneumonia ?

Certainly: Common symtoms of pneumonia include productive cough and fever. Viruses are always a possibility, but typically improve within 7-10 days. Pneumonia can be very dangerous...I suggest you see a doctor who may order a chest x-ray and perhaps some blood work. Interestingly, the color of mucus is a better indicator of hydration than infecton...But a week of worsening symptoms is always concering.

Yes: Pneumonia is an infection of the lower respiratory tract and usually causes shortness of breath, fever and productive cough. Pneumonia produces unusual sounds that can be detected by a stethoscope and confirmed by a chest x-ray. Please consider seeing your health care provider.