Poop is almost always brown when it's normal but sometimes it can be green even or other colors if you eat some foods in those colors.
If your poop changes from brown to another color and you haven't eaten any of those foods that could be that color then something could be wrong with your intestines or bowels.
If you have tinged blood red poop then it could mean that you're intestines are bleeding and you should see a doctor.
If the color of your stool or poop suddenly changes and doesn't change back to normal brown color then something could be wrong with your bowels or intestines and you should see a doctor for diagnoses of what it could actually be.