Yes, it's true! I bought some recently and bought the correct type of soil to re-pot them, but my mum got there first and used the wrong soil. I keep trying to get blue ones and they're all turning out pink!

I like all the colors hydrangeas come in...don't know if this is true, but someone told me the color depended on the acidity of the soil?

I adore hydrangeas. Mine didn't turn out this beautiful lilac-y blue colour, but they are bright pink which is pretty anyway.