Green stools are usually a sign of rapid transit or decreased colonic transit time. Basically, stomach contents passing too quickly through your system. The green is from bile and the color is visible because it hasn't had time to be absorbed as normal.
If a change in stool color can not be attributed to a dietary reason or is accompanied by any other symptoms (such as diarrhea, constipation, weakness, or dizziness) a doctor should be consulted immediately.
With the related chest pains etc. I would ask your doctor to check you for pancreatitis, pancreatic cancer, or a liver/biliary dysfunction. Check your afp, albumin, sgot/sgpt, ggtp and other lab values.
Good luck!!!