Thanks for pointing that out Harmy, I didn't even check Despecialized on that one. Your image came from the comparison image gallery, so I'll make sure to double check from now on. The real image is much better.

How do you think this shot was changed? I would guess that the background was isolated with a chroma key of some kind and then the color was swapped. This would mean that the original sky remains, it's just a different color. Or would the entire sky be replaced with something else? That doesn't make sense.