What causes lime green poop?

Normally, human fecal matter is semisolid with a mucus coating and brown coloration. This color comes from a combination of bile and bilirubin, which both come from dead red blood cells.

A green stool is usually the result of the rapid transit of food through the intestines, or more rarely the consumption of certain blue or green dyes in quantity.

There are also other forms of stools, including "clay-like," from a lack of bilirubin, stools with red streaks of blood, usually meaning bleeding from the rectum or anus (which can sometimes occur after constipation or anal sex), or black stools, indicating a serious problem in the intestines, as black is digested blood.

The rarest silver stool can occur when biliary obstruction of any type combines with gastrointestinal bleeding from any source. These symptoms can both result from a carcinoma of the ampulla of Vater.