I looked up a few images of M20 and the bottom nebula seems to be a bluish colour so using the lasso tool and isolating the bottom nebula I was able to tweak colour balance more towards the blue shade

I also used lasso tool to select only the center area with the dark nebula viens and tweak with sharpening, then I traced around the whole of the nebula top and bottom, selected inverse to only surround the background and stars, here I used selective colour and blacks, to make the sky blacker .

Steve