I would like very much to plant a Hydrangea and understand that the red mopheads do take sun. Can you confirm this?

Actually the mophead hydrangeas prefer some shade from the afternoon sun in our climate. In a west or south exposure the foliage can get scorched, particularly if the shrub is located against a fence or wall where there is reflected heat. Some dappled shade is ideal for them, and they will take morning sun just fine as well. Our alkaline soils do, however, tend to make the red and pink varieties especially vivid in colour.