Generally speaking, when you hack up a chunky phlegm-gobber, what color & texture is considered healthy, what’s considered not so great (but no action necessary) and what color should tell you to get thyself to a hospital forthwith? Taking into account factors like heavy smoking, illness, etc.
Please Note: I’m not asking for specific medical advice. My sputum (currently) is nice and clear, and I know that’s good. 
What my doctor has told me is that yellow means there’s an infection and white means the infection is gone and the body is just repairing the damage.
When I have bronchitis like now mine is yellow when I’m sick and white or clear when the sickness ends, so that seems to be in line with what Caligulas said.
http://www.mothernature.com/Library/Bookshelf/Books/16/207.cfm
Sputum colour is kind of unreliable. Thick white sputum may indicate asthma or inflammation; yellow or green may indicate an infection, but this could be viral or bacterial and does not necessarily require an antibiotic or hospital trip; smokers may cough up blacker sputum; rust coloured sputum may indicate Pseudomonas infection; blood tingeed sputum may be benign or a sign of bronchitis, tuberculosis or other conditions (google “hemoptysis” for a longer list).
Sputum is like temperature – it is probably worth relying on OTHER symptoms present at that time, rather than the colour (or temperature) itself.
Red is obviously a danger sign. Personally, I’d be concerned about stripes of any color, and paisly would worry me, too.
Unless, like me this morning, you had a nosebleed. 
Which, on some occasions, is something to worry about in and of itself.