I have seen many discolorations due to fungal infections but not pink. They tend to be reddish, orangeish, purplish, brownish or blackish. There is a carlavirus that affects blooms and deforms leaves but the resulting leaf discoloration is not pink. Do try posting a picture.

Here's a pic

Here is a link that might be useful: hydrangea

I had the same thing on one of my plants. It turned out to be a flower, a bit deformed but still a flower. This plant really struggled last year, I didnt water as much as I should have, so maybe that is what happened. The other flowers on the plant look normal.