This site page:
http://www.smugmug.com/help/skin-tone
might help you, though I don't see anything wrong with the color in your posted shot.
I can suggest that skin tone highlites are subject to several things, mainly color temp white balance of light source and skin color. The CMYK formula would start to appear close to neutral depending on the shine and the level of yellow would go up in all skintones going toward the shadows. Cyan is used for density and for turning caucasions brown.
Here's a quote off an Adobe Mac forum discussion from a prepress tech on his formula:
Caucasian skin tone=Yellow - highest / Magenta 10% less than yellow / Cyan 25% of yellow.