Hi,
your two lasts posts with Rally & Caterham look good. Maybe slight too blue sky sometimes.
It's always going to be a matter of how your eyes see it, and how a camera capture it. In the forest for example, the sky should be white because the camera has higher exposure due to the lack of light etc. that would require dynamic exposure throughout the race!
Then comes the question, how would you represent morning light ? On a camera setting point of view: Very dark to see the sky gradient, or very bright to see the road better but having a whiter sky ?
On another note, it's nice to have different options, depending on people's taste, but also depending on what screen rig you are using! I couldn't find anything good for my video projector, and i ended up going back to play in front of the pc screen...
As for the night/overcast atmosphere, i think you will be limited by the game engine, as the developers still didn't work on night and proper light effects.
that was my 2cents
All the best
-Ben