What does it mean when my 2 year old has the runs and its a dark green color?

Intestinal virus: Sounds like your little one has a "stimack flu" bug. These symtoms are usually caused by a virus - this time of year most common is rotavirus, could be others, ie noravirus. These are not viruses that are covered in any "yearly" flu shot - they are not influenza. Dark green is normal with these illnesses. That just reflects increased bile output by your liver and altered digestion with the illness.

Expected: The main agent adding color to the poo is the material made by the liver called bile. It starts out a dark green and goes thru the yellows to brown depending on the influences of various factors in the intestines. Rapid transit thru the system, as may occur with diarrhea or breast feeding may have a greenish yellow or yellow appearance. The slower, more likely browner.