This one I clicked the magic wand and clicked again to choose the sky area, then went to layers/gradient and chose blue. I then adjusted brightness on the whole shot to bring up the colours just a little. I also used the clone tool as in click on the tool, then I clicked on the sky blue and then painted over the green brush with some sky blue in the background.

Of course any postprocessing can be fine tuned or adjusted to personal taste. I am just trying to make you aware of the possibilities.

Tegan