The buildings in the images above from Keswick, Cumbria, England, are almost all green. In fact, the town of Keswick is almost all green. That's because the Lake District in which Keswick sits is the home of numerous quarries of green slate, or "greenslate" as it is known locally. These slates are largely the result of metamorphism of Early Paleozoic volcanogenic rocks. There are various shades of green in the slate, each with is local trade name, so there is some variation in the green of Keswick. The images above also show that stone masons trim the houses with red or brown stone, further enlivening the otherwise green visage of the town.
         

          

             The image below shows the greenslate up close. One stone at lower left appears to be neither green nor slate, but in fact it's the same green slate in which a fracture was filled with calcite. In quarrying, the stone broke along that fracture to leave the calcite surface visible in the image.