To enhance the mood and tune, I can think of 3 ways to do the foggy weather:
1. Download foggy png online to make a 3D card
2. Output Depth passes in CG to adjust grade and focus
Outputing CG with Depth passes to control the color grading, and Zfocus. However, in this scene, the background wind turbines are too tiny that, the result is not quite obvious.
3. Use Ramp in color correction in 2D layer
Simply add a Ramp on top of layers and control the handles to create gradient color.