I’ve put some of the sky in. I’ve used pinks, purples, a very pale yellow and blue for the sky. You also see that the barn has color along with the silos… What’s happening is the distance is being painted in. There is an absence of yellow with distance so purple values come into play. Yes the trees are green if you’re close to them but to create distance you have to consider the space between yourself and these distant trees which is full of atmosphere whit creates bluish trees. Next time your in the country and its foggy look at what’s around you and you’ll begin to understand what I’m saying.