What’s Up With This Hydrangea?

A few days ago my friend Blaire sent me the photo below with this question:

I am attaching a picture of my largest hydrangea bush. I love it, but for 2 or 3 years it has had pink AND blue flowers- fine with me- except i don’t know why.  I have seen others like this, so the soil is acidic and base?  One year it was pink and turned blue; acid rain?  Originally it was a pink plant.  I have a white bush next to it that stays white; a newer different species pink that has stayed pink and a container “blush” pink that has stayed that way.  Any ideas why the one bush does that?

So I’ve been looking for an answer to Blaire’s question and I really can’t find one. There’s plenty of information on the basic concept that acidic soil produces blue flowers while alkaline soil produces pink. There’s also lots of information about how to change flower color and what species of plants favor each color. I’m curious now too about what would cause a consistant multi-colored bloom.

What do you think? Help us solve the mystery!

What’s up with Blaire’s hydrangea?