Fix extreme color cast resulting from:

    1.  Color temperature is set to a wrong value.

    2.  Old color photos that have become faded.

PROCESS:

    1.  Create a copy of the Background image layer by dragging that layer to the Create a New Layer button at the bottom of the Layers palette.

          (determine color of color cast)

    2.  Select Filter > Blur > Average 

         (this is  problem color, determine the opposite)

    3.  Image > Adjustments > Invert

    4.  Set blend mode to Color using the dropdown at the top-left of the Layers palette

    5.  To tone down correction, use Opacity slider

    6.  Boost saturation (using a Hue/Saturation adjustment layer)