Andre has been playing with the fog. He didn't explain what he'd done in time for this devblog though, so I'm going to make it up base don overheard conversations. Normal fog, our old fog, is a single colour which gets stronger based on the distance from the camera. This new fog is per pixel and takes the environment into consideration. So it's a different colour depending on where the sun is relative to the pixel you're looking at.
It's got horizon clouds now too - which soften the join between the horizon and the land.