Healthy stool is medium brown, roughly the color of milk chocolate or a cardboard box. This shade comes from a pigment called stercobilin, which forms when your liver, bile, and gut bacteria work together to break down old red blood cells. A range of browns is perfectly normal, from light tan to a darker walnut, and the exact shade can shift day to day based on what you eat and drink. Colors outside the brown family, like red, black, pale white, or persistent green or yellow, can signal anything from a harmless dietary quirk to something worth investigating.
Why Stool Is Brown
The brown color starts with your liver. When red blood cells reach the end of their roughly 120-day lifespan, your body breaks them down and produces a yellow-green substance called bilirubin. Your liver sends bilirubin into the small intestine through bile. Once in the gut, bacteria convert bilirubin into a compound called urobilinogen, which then oxidizes into stercobilin, a dark orange pigment. Stercobilin mixes with the digested food, fiber, and water that make up stool, producing the familiar brown.
Anything that changes how much bile reaches your intestines, how quickly food moves through, or what you’ve recently eaten can shift the shade. That’s why one unusual color after a big salad or a new supplement is rarely a concern on its own.
What Green Stool Means
Green stool is one of the most common color variations, and it’s usually harmless. Bile itself starts out green before gut bacteria convert it to brown. If food passes through your large intestine faster than usual, as happens during a bout of diarrhea, bile doesn’t have time to fully break down, and stool stays green.
Diet is the other big driver. Large servings of spinach, kale, or other leafy greens can tint stool noticeably. Green food coloring in drink mixes, ice pops, or frosting does the same. Iron supplements are another frequent culprit, sometimes producing a dark green that borders on black. If your stool turns green after any of these and returns to brown within a day or two, there’s nothing to worry about.
What Red Stool Means
Red stool gets more attention because it can look like blood, and sometimes it is. But plenty of foods cause the same appearance. Beets are the classic example, turning stool (and urine) a startling reddish-pink. Tomatoes, cranberries, and anything with red food coloring can do it too. If you ate one of these foods in the last day or two, that’s the likely explanation.
When the red color actually is blood, the shade and location offer clues. Bright red blood on the surface of stool, on toilet paper, or in the bowl typically points to bleeding in the lower digestive tract, near the rectum or anus. The most common cause in adults is hemorrhoids, swollen blood vessels triggered by straining, chronic constipation, or prolonged sitting. Anal fissures, small tears in the skin around the anus, are another frequent source and tend to cause sharp pain during a bowel movement along with streaks of bright red.
Less common but more serious causes include diverticulosis (small pouches in the colon wall whose blood vessels can rupture), inflammatory bowel disease like Crohn’s or ulcerative colitis, colon polyps, and colorectal cancer. Colorectal cancer may also bring changes in bowel habits, unexplained weight loss, and fatigue. Red stool that can’t be traced to food, or that comes with pain, cramping, or diarrhea, is worth getting checked promptly.
What Black Stool Means
Black stool falls into two very different categories: harmless and urgent. On the harmless side, Pepto-Bismol (bismuth subsalicylate) is notorious for turning stool jet black. Iron supplements, activated charcoal, black licorice, blueberries, and blood sausage can all do the same.
The concerning version is called melena: stool that is not only black but tarry, sticky, and foul-smelling. Melena signals bleeding in the upper digestive tract, typically the esophagus, stomach, or the first section of the small intestine. The blood appears black rather than red because it gets partially digested as it travels through the gut. If you see black, tarry stool and you haven’t taken any of the foods or medications listed above, that’s a reason to seek medical attention quickly. A simple chemical test can confirm whether blood is present.
What Pale or Clay-Colored Stool Means
Stool that looks pale, clay-colored, or putty-like is one of the more medically significant color changes. Remember that bile salts are what give stool its brown pigment. When bile production drops or bile can’t flow from the liver into the intestine, stool loses that color entirely.
The most common reasons bile gets blocked or reduced include gallstones lodged in a bile duct, liver infections like viral hepatitis, alcoholic hepatitis, cirrhosis, and tumors in the liver, bile ducts, or pancreas. Certain medications can also temporarily reduce bile flow. Pale stool that persists for more than a day or two, especially if paired with dark urine, yellowing skin, or abdominal pain, points to a problem in the liver, gallbladder, or pancreas that needs evaluation.
What Yellow, Greasy Stool Means
Yellow stool that is also bulky, greasy, foul-smelling, and hard to flush is a sign that your body isn’t absorbing fat properly. This condition is called steatorrhea. Fat passes through undigested, giving stool a pale, oily appearance. It often floats because of its high fat content.
Two of the most common underlying causes are celiac disease, where gluten triggers an immune reaction that damages the lining of the small intestine, and pancreatic insufficiency, where the pancreas can’t produce enough digestive enzymes to break down fat. If you’re regularly seeing yellow, greasy stools along with bloating, weight loss, or foul-smelling gas, it’s a pattern worth discussing with a healthcare provider. Occasional yellow stool after a particularly high-fat meal, on the other hand, is less concerning.
Normal Stool Colors in Babies
Infant stool follows its own color timeline and can alarm new parents who aren’t expecting it. A newborn’s first few bowel movements are meconium: thick, sticky, and black or dark green. This is completely normal and clears within the first few days of life.
After meconium passes, color depends largely on feeding. Breastfed babies typically produce mustardy yellow stool, sometimes with a seedy texture. Formula-fed babies tend toward yellow-tan with hints of green. Both are healthy. As solid foods are introduced, stool gradually shifts toward the standard brown range, though it can temporarily take on the color of whatever the baby ate (orange after sweet potatoes, for example). The colors to watch for in infants are the same as in adults: persistent white or clay-colored stool, red, or black stool after the meconium stage.
When a Color Change Matters
A single off-color stool after an unusual meal, a new supplement, or an over-the-counter medication is almost always benign. The more useful question is whether the change persists. Stool that doesn’t return to brown within a few days, or that changes colors repeatedly without an obvious dietary explanation, deserves attention. The same goes for any color change accompanied by fever, diarrhea, abdominal pain, unexplained weight loss, or visible mucus. In those cases, the color is one piece of a larger picture your provider can help interpret.