The Poop Color Chart

Poop is brown because of bile: a pigment your liver makes from old red blood cells travels into the gut, where bacteria turn it brown. Most changes in color trace back to something you ate, a medicine, or how fast stool moved through you. Green, yellow and orange usually fall into that category. Three colors deserve more attention: red and black, because they can mean blood, and pale or clay, because it can mean bile is not reaching the stool.

See more than color: Stoolio reads color alongside your Bristol type and 12 visual readings from one photo, and keeps a dated record so a color that sticks around stands out. Your first three scans are free.

Why is poop brown?

It starts with red blood cells. When they reach the end of their life, the body breaks down their hemoglobin into bilirubin, a yellow pigment. The liver sends bilirubin into the gut in bile, the yellow-green fluid that helps digest fat. In the colon, gut bacteria convert bilirubin into urobilinogen, and most of that leaves the body as stercobilin. MedlinePlus and Cleveland Clinic both put it plainly: bile and the bilirubin it carries give stool its normal brown color. In 2024, researchers identified the bacterial enzyme that starts that conversion; it is found in nearly all healthy adults but less often in newborns.

That chain explains most color changes. If stool moves too fast, bile does not have time to finish changing and stool can look green or yellow. If bile does not reach the gut at all, stool turns pale. And if something with a strong color of its own is added, like beets, iron or food dye, it can override the brown.

The seven colors at a glance

Most color changes come from food

Cleveland Clinic's summary is that most of the time, the color of your poop points to something you ate. Mayo Clinic adds that only rarely does stool color indicate a possibly serious intestinal condition. Both lists of food causes are long: leafy greens and green drink mixes for green; carrots, sweet potatoes and squash for orange and yellow; beets, tomato juice and red gelatin for red; black licorice and blueberries for black. A 2021 study in the journal Gut used exactly this effect on purpose, giving 863 people blue-dyed muffins and timing how long the color took to appear.

A food-driven tint should fade once the food is out of your system, usually within a day or two, though it can take a few days. If a new color shows up and you feel fine and do not have diarrhea, Cleveland Clinic's gastroenterologist notes that it most likely stems from something you ate.

Transit: why speed changes color

Bile starts out yellow-green and is chemically changed on its way through the gut. When food moves through the large intestine too quickly, as with diarrhea, Mayo Clinic explains, bile does not have time to break down completely, and stool can come out green. Fast transit can also leave stool yellow. That is why color and shape often change together: a loose, green stool usually means a fast day, not a green meal. See the Bristol stool chart for what shape says about speed.

The three colors that deserve attention

• Red, because it can be blood. Bright red usually means bleeding low in the colon, rectum or anus, most commonly from hemorrhoids or small tears called fissures. Beets and red dyes are common harmless causes, but any blood you cannot explain deserves a check-in with a clinician.
• Black, because black, tarry, sticky stool can mean bleeding higher in the gut, such as from a stomach ulcer. Iron and bismuth darken stool too, but that does not rule bleeding out: black and tarry stool needs same-day medical care.
• Pale or clay, because stool that loses its color may mean bile is not reaching it, from a blocked bile duct or a liver problem. A single pale stool is rarely remarkable; pale for more than a few days, or with yellow skin or dark urine, needs a clinician. In babies, pale or white stool needs a prompt call to the pediatrician.

For any other unusual color, the general rule from MedlinePlus and Cleveland Clinic is to contact a healthcare provider if your stool does not go back to brown within a few days, or sooner if it comes with symptoms such as pain, fever or weight loss.

Why color is hard to judge by eye

Color is harder to read than it sounds. Dark green can pass for black in poor light, which is why pediatric guidance suggests smearing a sample on white paper and looking under bright light. In a study of infant stool photos, doctors and nurses misidentified about a third of them, which is the reason some countries give new parents printed stool color cards. For adults, the practical advice is simple: good light, a clear look, and a record, so you are comparing today with your own normal instead of with memory.

What Stoolio looks at visually

Every Stoolio scan includes a Color Assessment that places your stool on six shades: pale, light brown, brown, dark brown, green and very dark. It sits alongside your Bristol type, a Stoolio Score and the rest of the 12 visual readings, including shape, size, consistency and fragmentation, and each one is tracked over time. That is where color becomes useful: one green stool is trivia, but three days of very dark readings in a row is a pattern you will not miss.

A scan is a visual estimate, not a lab test. It cannot detect blood that is invisible to the eye (that is what stool blood tests are for), and it cannot tell iron-darkened stool from bleeding. If you ever see red, black and tarry, or persistently pale stool, talk to a clinician rather than waiting on an app. Read how a scan compares with lab tests, or try the free What does my poop mean? checker.

Sources

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