It's not a pleasant topic, but it's one that requires our attention. Your poop tells you everything you need to know about your overall health, especially what's going on in your digestive system. Although there's not necessarily a one-poop-fits-all rule to live by, a standard healthy poop is sausage-like and "S"-shaped, and generally it should sink. Your poop will certainly vary from day to day depending on what you've been eating and drinking, but this is the kind of stool you should be aiming for.
The consistency of your poop matters, but it isn't the only thing you should be looking at. The colour matters, too. Here's a basic guide to judging the colour of your stool.
Generally, black poop isn't something to worry too much about, particularly if it's a one-off thing. Some foods you eat can cause your stool to turn a dark, scary colour, such as black licorice, too many blueberries, or Pepto-Bismol. However, if your poop is consistently black and you can't figure out why, you should probably go see a doctor. It might mean you have bleeding in your upper gastrointestinal tract.
This could mean a few things. Your bile ducts could be blocked, your pancreas might not be secreting enough enzymes for digestion, or you could be having trouble processing gluten and you might have celiac disease. Don't let yellow poop go unnoticed, especially if it's showing up more often than not. It could be a sign of internal trouble.
You might look at green stool and just chalk it up to eating a lot of spinach or kale, and that could certainly be the case, but leafy greens aren't the only culprit. Green poop can also happen when food moves through your intestines too quickly and isn't processed fully by the bile in your body. Iron supplements and other foods might give you green stool as well. Whatever the case may be, green poop is generally nothing to worry about.
There are two kinds of red poops you should know about. The first is completely harmless, as it's likely from having one too many beet juices or desserts that feature some kind of red food colouring. However, the other kind is when blood is in your stool, and that's not a good thing. It could mean a few different things, from internal hemorrhaging to an anal fissure. It might even indicate a type of undiagnosed cancer. If you can't pinpoint it to something you ate and you just keep seeing red in your toilet bowl, chat with your doctor ASAP.
Light Coloured or Grey
A lighter shade of poop, whether it's clay-like or grey, means there isn't enough bile in your poop, which could indicate a bile duct obstruction. This calls for a visit to your doctor. Then again, light-coloured stool might show up if you're taking certain medications or recently took an antidiarrheal drug. The general rule of thumb is if it shows up consistently, it's worth talking to a medical professional about.