Does normal stool change the color of the bottom of the toilet water if left sitting there for a long time? is this blood or am i overthinking?

If you have any concern you can have your stool tested for occult blood. You could buy a kit at your pharmacy for the test, or your doctor could order the test. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs.