Yes. Coffee grounds are rich in nitrogen, which promotes foliar growth. They also boost acidity in the soil, making it easier for plants to absorb the aluminum that's in the soil, leading to blue blooms.
In addition to providing nutrients, eggshells can help your hydrangeas develop pink blooms. This happens because when they break down, egg shells reduce acidity in soil. When the soil pH is high, hydrangeas do not absorb aluminum easily. The lack of aluminum causes the plants to yield pink blooms.