I was hospitalized twice for pneumonia. First time I was released I was still only coughing up clear fluid. The second time still had color. Color is caused by a natural process when white blood cells are fighting an invader and depth of color can depend on how concentrated the phlegm is before you see it. It is not a reflection or indication of any inflection by itself. It should fade back to normal in a couple of days.

One can assume that your inflammation, amount of fluid, and whatever caused the pneumonia in the first place is under-control or they would not have released you. So I wouldnt worry too much about it, unless it gets worse and you also start to re-develop the symptoms that put you into the hospital before. If that happens call them back.

I agree with Gnott. Unless you are coughing constantly, and having pain or some other symptom, do not worry, just keep it coming up and out. After a few days, if it does not go away, or if symptoms get worse, call your doctor.
BJ