Experts and BHG readers answer.
Thanks for writing. If you want truly pink blooms, select varieties such as 'Forever Pink' or 'Pink Shira' that keep a pink base to the flower tone. Then check your soil; most mophead and lacecap flowers lean toward pink shades in alkaline soil and blue shades in acidic soil. So if your soil is acidic, you'll want to add a bit of dolomitic lime to help raise the pH.
It can be difficult to grow pink and blue hydrangeas near each other because you'll need to treat the soil differently to produce those bloom colors. The closer they are together, the more likely they are to be affected by the soil treatment you give the other one (meaning the pink one will develop muddy blue tones and the blue one will develop muddy pink shades).
---Justin, Senior Garden Editor, BHG.com