You know, I'm not an expert, but I don't think that it is always dried
blood.  That was, until recently, my usual color both from my sinuses
and when I coughed it up from my lungs unless I have an acute infection
and then it is yellow or green.  Mine was a dark brown.  My mom was a
smoker and has COPD and coughs up a tannish mucus, but I've never seen
it dark brown.  I showed mine to one of my doctors and he said it
looked like pneumonia.  On the other hand, I had a mold cultured from
it a couple of times, and there are many molds that can make it dark
brown, and a particular disase called allergic pulmonary aspergillosis.
I'm sure that dried blood would also make it look brownish.  
Kathyw

It's brain puss

Shirley a écrit :

No, it can be badly infected secretions.

I used to cough up brown gunk before I had my sinus surgery.

But if you're a smoker, you really should see a physician ASAP.