in this tutorial i will show you how to Get back original colors of the photograph with HOLD ALT [Use ALT instead of OPTION for MAC] technique.
1) First open image background layer.
2) select curves from adjustments.
3) Select dark eye dropper and place it in dark area.
4) Similarly take grey and white eye dropper and place it in desire area.
5) Hold ALT when selected eye dropper it helps to easy find the dark, grey and white areas.
6) HOLD ALT shows red colors in image means it is bright area in image.
7) Check the above video tutorial to see detailed view.
8) Here is final before and after results.