One way of knowing if you need to water your hydrangeas is to check them in the morning before the sun has started to heat them up. If the leaves are already starting to droop they need water. Conversely, just because the leaves are drooping in late afternoon it doesn't mean they need to be watered. You can also feel the soil and if it's dry at 2" it needs to be watered and you can clean your dirty hands as you water them.

What is needed to have blue flowers for your macrophylia hydrangeas? An acidic (ph 4.5-6.0) soil will result in a blue flower. The acidic ph releases aluminum in the soil which makes the blue flower. If color is purple to pink or red add aluminum silicate per instructions on the container to drive the ph down. Pine needles around the plant will also help lower the ph. If you want pink or red instead of blue add lime to the soil. this will move the ph up to basic and retard the aluminum from getting into the plant.