Infection phlegm is green... always green. Think like infection pus is green (helpful image, eh? ;-)

Brown phlegm is (as mentioned above) dried blood mixed in. Coughing up blood of any kind is worrisome, but I agree with previous assessment that it's probably because you've damaged tissues from coughing so hard.

If your cough sounds like a "seal bark" then it's a good sign that it's bronchitis or the ilk. Ugh.

(just my two cents *clink clink*)