I can't say the pink Klingon blood made much sense. . .
I think that was done to avoid a PG-13 rating, which could have reduced box office results.
No, no, no, no, no. God, I wish this silly rumor would go away.

From Meyer's memoir, years after the fact.
"There was a debate over the color of blood, which I wanted to be different than human blood. I wound up choosing a pink shade that seemed suitably weird, only to regret my choice down the road when I realized it reminded me of Pepto Bismol."
--Nicholas Meyer, The View From the Bridge, p.217