Do you have any symptoms like tightness or rattling in the chest, any breathing problems? This, together with what you have coughed up would indicate a problem with the lungs and you should see a doctor urgently.
I presume that you have not eaten anything that was dark in colour that could have discoloured the mucus. If you have not eaten anything that could make your mucus a dark colour (coffee, chocolate), it would be wise to get seen to by the doctor.
In the meantime, make sure that you drink plenty of warm fluids (avoid milk whilst you have lots of mucus) and stay warm. Wrap a scarf around your mouth and nose so that you do not breathe in the cold air when you go outside.
Let us know how you get on.
It could be a sign of Bronchitis or pneumonia. I would go to the Urgent Care and see what they can do. Possibly a chest x-ray to find out if you have bronchitis or pneumonia. If they find something, they will put you on an antibiotic. Like me, I'm still trying to fight off my bronchitis, and they put me on Zithromax (Z-pack). But I would definitely go to the urgent care or see your PCP first.
I would go in to the er or urgent care. Show them the pic and ask. It looks like what I was hacking up when I was fighting bronchitis and double pmnuemonia(sp?)