A bit of contrast to add power, brightness, strength to the sky, to the trees. Hmm... And the red-leaf trees on the right are in contradiction or completion with two shades of blue, the dark blue, the sky, and the light blue, the water from the right side of the image. The left side, a combination of green and yellow, but much more alive than the other side, which denotes coldness. Hm... I like the Yin/Yang, masculine/feminine imagery in this photo. Nice shot by the way.