Background color wash for Young trees drawing

For the picture itself, I indicated the horizon line on a half-sheet (22" x 15") 140 lb watercolor paper and masked out the crescent moon to keep it white. The finished drawing itself will be 12" x 17". Then I wetted the paper and put in blue at the top, fading out toward the horizon and added a touch of red and yellow near the horizon. The snow in the forground got a pale layer of blue.