Thanks for the question.
This certainly is concerning and you need to see your doctor.
Bile is green.
Or yellow when vomited.
What concerns me here is that brown, in addition to food, might reflect minor bleeding.
If you are getting this from the lungs, then serious infection.
This cough could be pneumonia, and one can walk around with atypical pneumonia until it is a real problem.
This is serious enough that I would recommend you go to A&E now.
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Yes, my answer and recommendation are the same.
Did you have another question?
Not likely unless you are smoker, then possible.
Then you should have a CT [high resolution] of the lungs.
X ray is OK, but not at good.