Pink or blue?

The flowers of this Hydrangea bush were blue three years ago, when I first bought it.

They have all turned pink because my soil is too alkaline.   I have been feeding it a special fertilizer to turn the blooms back to blue, but as of yet I have had no luck .

When it first blooms, the flower is pale pink and green,   It becomes a brighter more vibrant pink as it matures.