Any of them
In vomitus, active brisk bleeding may look like a unit of transfused blood.
If this is what you're seeing, call 911 immediately.Old blood may look like coffee-grounds, and be dark-colored. Oozing, small volume bleeds may be diluted by other stomach contents and may look like streaks, clots, or pink-tinged material. Any of these descriptions deserves urgent evaluation--bleeding is never "normal.".