In the photo here you can see a slight yellow tint in the skin tone. I will show you a few quick and simple techniques to adjust the skins tone.
First technique we are going to use swatches.
Select your eye drop tool.
and Find a few places on the skin that have a true skin color (or use a another photo with correct skin color).
After you select an area, to make a new Swatch go to Windows>Swatches. In the Swatch palette select the "Create new swatch".
Make a few so that later on you can have a few options and see which one works the best.
Now on your layer palette select "Create a new layer" and set the blend mode to Color.
After that select your brush tool
and paint over the skin. You should see the skin tones become more original and the yellow being removed.
Play with different color swatches to find what works best for you.
The next technique uses a few less steps but is not always accurate. It primely depends on the colors in the photo and the tones being changes. Sometimes this doesn't always work correctly.
Go to Image>Adjustments>Selective color
Sence Yellow is the tone we are trying to remove we are going to select the color yellow in the Selective Color menu and then move the yellow slide bar all the way down (to the left) and the you can adjust the other colors for your liking.
And there we have it.
I hope you enjoyed the tutorial.