In most species the flowers are white but in some  can be blue, red, pink, or purple. In these  the exact color often depends on the phof the soil' soils rich in acid produce blue flowers, neutral soils produce very pale cream petals, and alkaline soils results in pink or purple. Hydrangeas are one of very few plants that accumulate aluminium. Aluminium is released from acidic soils, and in some species, forms complexes in the hydrangea flower giving them their blue colour.

So how did I get a pinkish purple flowering hydrangea as pictured above?

Right next to it is the blue.....

Both are equally beautiful but how can the soil change be so different when they are right next to each other?