Graduation Filtering

Original picture

Filtered Layer

Final

Other Colour
The orginal picture has a washed-out sky. I gave it a warmer tone by doing the following:
  • Create a duplicate layer.
  • Select the channel mixer Filters>Colors>Channel Mixer.
  • Leave Red channel unchanged.
  • Set the Green channel to red=0, green=80, blue=0.
  • Set the Blue channel to red=0, green=0, blue=60.
  • Add a layer-mask to the duplicate layer.
  • Apply a graduation fill to the layer-mask.
  • The other image was created using the red and green channels reduced to 70, and the blue remaining on 100.
A script I wrote to automate this process is here.