The shade of your stool
-Brown
If your poop is brown, then you are fin. Poop is brown due to the bile produced in your liver.

-Green
Maybe you have eaten a lot of green leafy veggies or green food coloring. The food might be going through your large intestine too quickly.

-Yellow
This type of poop indicates excess fat. This is because of malabsorption disorder like celiac disease.

Black
This means that you are bleeding internally, because of ulcer or cancer. It may be caused by some vitamins that contain iron or bismuth subsalicylate. You should see a doctor if you are worried about this.