The goal in a landscape painting is to create the sense of space.
Colors generally follow a prismatic progression from foreground to background.
Background colors should be on the blue/indigo/violet range of the spectrum with a bit of cool red added. Objects are smaller, have less contrast, are closer together (as in a fence) and have softer edges that blend together.
Foreground colors are green, yellow, red or ohre. Objects are larger and have contrast, texture and clarity.
** My thoughts. When riding in a car I am always looking at objects in relationship to one another, colors, clouds, and especially the look of a background, and take notes. I have a notepad and pencil in my purse where I jot down things as they come to me. For some reason when I am in a car sight takes over and my mind becomes the receiver as the secondary function and I love to become quiet and thoughtful. Riding is very relaxing.
I have also read/heard that if you use a color on one side of a landscape you should incorporate the color into the other side so that you have balance...and mix cool and warm colors for floral accents.