I go by amount, not color. My GI bleed was bright red and I ended up losing massive amounts of blood. The blood changes to a darker color the longer it takes to move out of your body. If your bleeding very heavily, it won't have a chance to turn dark. Mine never did.
My bleed was just pure blood and tons and tons of it. It was like having several giant bouts of D, but with nothing but blood. Quite scary! I would have died had I not been hospitalized, with them going in and stopping the bleed by colonoscopy. I had many months on iron supplements, and could barely get from one room to the other in my house without being out of breath. I think it's always a good idea to make sure the doctors know about
it. Even if it's just some bleeding every day, it can add up and make us pretty anemic. With MASSIVE bleeding I get myself to an ER.