jessem,

i smoked cigarettes for years before smoking pot. i had dark/grey phlegm coming out in my morning shower. after i started smoking joints (mmc for IBS), my lungs felt better, but the stuff was still dark/grey.

then i quit smoking cigarettes. my phlegm turned from grey to green (i'm high 24/7) and my lungs started feeling even better.

anyhoo, my 2 cents is that if your phlegm is dark/grey, its NOT the pot.

i hope this helps...

b