This moring I had diarea and then about an hour later I threw up. What do you think this could be? What does it mean if the stool is a dark green?

A few possibilities. Usually diarrhea and vomiting are signs of gastroenteritis (viral). However green stool can indicate gallbladder disease or other infectious intestinal problems. Possible blockage of the intestine is also seen with vomiting and diarrhea. I would advise you to see your physician to get properly tested.
More info. If you have recently been in antibiotics, then this could be diarrhea caused by an overgrowth of bacteria called c. Diff. If this is the case, you need to go back to your doc right away. If you haven't then it could simply be viral gastroenteritis. More info is needed to know. Either way, you should see your doc.