Hydrangea blooms

I have always been told the color of hydrangea blooms comes from the type of soil. Always had my doubts, due to moving the same plant to 4 different locations in East Tennessee and the blooms stayed blue. These 3 photos were taken outside my daughter's office window. Notice the pink and the blue blooms are so close to each other they can be seen in the same photo.
Hydrangea are another of my favorites, due to the first ones I remember were at my Granny Sorrells' house.