There are several different hydrangeas that have pink blooms. Most common are hydrangea macrophylla. For those shrubs, the color of the blooms is determined by pH in the soil. The more alkaline the soil is, the pinker the flowers will typically turn. In order to turn the soil more alkaline you can add wood ash to the soil. This is generally a slow process though, and can take a year or two to change the color. This group can also include mountain hydrangeas (hydrangea serrata), but these are far less common than macrophylla.
Other pink hydrangeas that are available to grow will start white then turn to pink as the blooms get older in the summer and fall. Typically these are either smooth hydrangeas (hydrangea arborescens), or panicle hydrangeas (hydrangea paniculata).
Pink Hydrangea Meaning
Pink hydrangeas symbolize heartfelt emotions and romance because flowers resemble a beating heart. It can also be linked to love, weddings, and marriage.