Bring up very dark green stuff when brush teeth??

I neb twice a day. Most of the time I bring up light or maybe medium colored sputum. I have colonized pseudomonas (and MAC in remission.) When I brush my teeth I bring up very dark green ?sputum. I originally thought it was sinus drainage but I'm not having any sinus problems. I'm now not sure and wondering if any others experience this. Thanks.