I design billboards using XaraX.
I use a digital photo of an existing board and put the proposed customers graphics on it.
My problem is that here in Oklahoma the air is usually thick and hazy. This makes the sky more of a hazy gray instead of blue.
I would like to replace the sky with a nicer (bluer) one. I can crop the sky out, but there is normally a tree line which makes for somewhat tedious node editing. Is there a way to select the sky with something like the magic wand tool, or select just a range of colors to replace?

Thanks for any help.