This is Laguna canyon. I've painted this general area before and have tried this scene. In the early morning the sun is off to the left, leaving the back hills with shadows. Plus there is usually clouds or fog lifting which puts moisture in the air, emphasizing the blue in the background hills. When I started this piece I felt the blue of the hills was an important key note to get in to be able to judge all the other colors and values off of. So after drawing in my basic line composition, I filled the whole background hill shape with the blue color of the shadow. Then I came back over top with a bit thicker paint in the green color to create the trees and foliage coming down the hills. A little bit thicker paint at each of the ridges, then dry brush dragging some of the paint over more of the hill area. This covered up some of the blue, but not all, thereby creating slight variations in value by being able to see the blue and the green.