“In our first image, we want to start on the landscape with our basic colour palette. Ideally, I like to start off with my background layer first which would be in our case, the clouds. So here I’m going to think about what colour scheme I wanted for the image, something cold, warm, hot, or dark .”
http://www.3dtotal.com/team/Tutorials_3/painting_a_landscape/painting_a_landscape01.php