The pinkish tint can also be from food - anything from dye in kibble to red fish etc.
All I can say is when Yittle threw up blood, we knew with absolute certainty thats what we were looking at. Ditto for one of our other cats back many years ago. Yittle was sick, but he recovered. The other cat years ago it turned out that she'd just thrown up so much that week with hairballs that she'd ruptured a tiny blood vessel somewhere... the quantity thrown up was minute and of no danger to her. Its not THAT uncommon for that to happen.