They are Hydrangeas macrophyllas. I was told that, on the left, the light blue is a free-flowering mophead, called "Générale Vicomtesse de Vibraye" In the back and the front, three "Nikko blue". One of them, for some unknown reason, became purple over the years. The leaves of the Nikko are thicker and greener that the first specie. They all blossom abundantly if they are well watered and not planted in full shade.

What is the plant in the foreground, in the left corner of the picture, please?

It's a rhododendron. It had finished blooming for the season, but keeps its green leaves all year round..