Contrast. It's out there all around.
I didn't realize how much contrast I was dealing with until I started to get into it. As I set out my paints, I thought "Today I'm working with the contrast of complementary colors - the pink of the fireweed flowers against the green of the foliage."
Well, fine, but then there's the contrast of the small size of the pink area and all those masses of greens, and the contrast of the highlights in yellow-greens against the dark-olive shadows. And the contrast of the horizontal curves of the branches against the vertical curves of the stems and leaves. And the thickness of the tree trunk against those same slender stems.
Contrast? I got a lot more of it than I had bargained for... and you know the best part? The next time I go looking for contrast in a scene to paint, I will probably find even more to play with.