If your diarrhea is a cloudy yellow, then your colonoscopy prep isn’t over. He is the founder of retroflexions.com and enjoys writing about healthy living and the practice of medicine. Find Out More Information Regarding Alternative Natural Preparations For Your Colonoscopy Read The Detailed Description Colonoscopy Prep Colonoscopy Prepping He started his solo practice, precision digestive care, in 2018. Why is my colonoscopy prep yellow . The colonoscopy itself is a snap! I think he said it was hard to see, so it must have been cloudy. The yellow color is from bile stain. I took the first suprep at 6pm. Clear liquid is any liquid that you can see through. The stool before a colonoscopy should be a yellowish clear liquid. I have been on aspirin therapy for my heart. The yellow actually is from bile, and not unusual. Colonoscopy checklist download this easy checklist so you don't forget. So, before rushing to the conclusion for your bowel movements, yo...