IMHO depends on the amount. If you are severely dehydrated and you notice your stool physically hurt coming out. A small amount of blood might honestly not be unexpected.
Edit: To be clear “severely dehydrated” is kinda an important factor here. Point being that if the cause is obvious I dont see why you’d get a colonoscopy. Please correct me if im wrong instead of just downvoting for anyone who knows more about this thx ^^