Hydrangeas can go from Deep Blue to Hot Pink just by changing the pH of the soil. It may take a matter of months, but it can be achieved with soil amendments. A sulfur or nitrogen based amendment such as Holly-tone will lower the number; acidic= blue blooms. A limestone based amendment like Plant-tone will raise the number and make the soil more alkaline resulting in pink blooms.*It is important to get a soil test before you begin treatment and make sure surrounding plant material can handle the pH adjustment.