You haven't given us any information to go on - what is your gardening zone and which type hydrangea. Most macrophylla prefer some protection from mid day sun but do OK with very little shade here in my maritime climate, the paniculata or pee gee types will take stronger light. The brightness conditions range of serrata can run from dense shade to just about full sun conditions depending on which cultivar.

Your gardening zone or area, and which plant are you considering, please?

Sun or shade. Yes.