What color is normal stool? What does it mean to change to red, green, yellow, and gray?

 German Professor Thomas Zufferlein said that the normal color of stool is medium brown, noting that changes in stool color raise the alarm.

The gastroenterologist explained that the stool color changes mean the following:

1- The red color portends hemorrhoids or anal rupture due to constipation or colon cancer.

2- The green color indicates salmonella infection, especially when suffering from severe diarrhea.

3- Yellow indicates problems with the pancreas or intolerance to gluten.

4- Gray color indicates gallstones or pancreatic tumors.