Here is a method that I have used. Find an image of a face that is similar (lighting etc.).
Add a solid color adjustment layer (any neutral color for now) and set it to
color mode.
Fill the mask with black and make a selection over the area you want to color match, fill selection with white. You will now see a mismatched color square over your sample image.
Zoom into the sample area.
Double click the solid color layer to bring up the color picker, then adjust the color until your patch area disappears (close as you can get).
You have your first color.
Do the same for various areas until you develop a complete color palette.
Name the colors for the areas to which they correspond and save the collection in your color library.
Obviously the colors will need some tweaking for each individual image, but they are a good starting point. You can also alter the opacity if required.