Janice Parker calls it “jardin vert,” or green garden. But this property, which includes a 1920s house on 6 acres and a new equestrian facility by Jones Byrne Margeotes Partners on the adjacent 10, is anything but monochromatic. The green tones run the gamut: Not only are there gradations in leaf hue but also the tree bark ranges from the gray of beeches to the dark brown of sugar maples.