Good morning doctors. what may cause blackish stool other than colon cancer?

Consumption can influence stool color. In this case bismuth salicylate or Pepto Bismol is one common trigger to dark/black poop.

Diet, meds and non specific bleeding from upper gi tract are commonly involved in changing stool color in black. Not all black stools are due to bleeding and black stools are not diagnostic for specific pathology, such as cancer. Your gastroenterologist or PCP would be best to place your findings in clinical context.