This is what a Hydrangea bush looks like to a 4 year old. My son took this photo and I think he did a great job!
We were walking past this lovely corner garden filled with blooming Hydrangeas. Upon closer inspection, I realized the color shift in the blooms. Have a look:
The flowers on the far side of the photo are deep blue and the ones closer to me are more lavender color (the true purple flowers are a separate plant and cultivar altogether). To get blue Hydrangeas to turn pink, one can amend the soil with lime to make it more alkaline. So it would seem that the soil pH changes right under these bushes!
This photo shows that even the flower head itself is two different colors: