Causes of black colored stools(known as melena)
acidified blood
blood from higher in the digestive tract
iron supplements or foods high in iron
Pepto Bismol or other medicines containing bismuth
black licorice
large amounts of spinach or other greens
blueberries
aspirin
other foods dark in color such as chocolate sandwich cookies (Oreos)
Causes of red colored stools (known as hematochezia)
blood
hemorrhoids
red gelatin, popsicles, or Kool-Aid
tomato juice or soup
large amounts beets
Causes of pale or clay colored stools
lack of bile salt (which gives stool a brownish color)
antacids containing aluminum hydroxide
barium from recent barium enema test
hepatitis
Causes of green stools
large amounts of green, leafy vegetables
green or purple artificial coloring (popsicles, Kool-Aid, gelatin)
iron supplements
rapid transit or decreased colonic transit time
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.