Assuming the model is not in shadow or a light with color cast, skin colors can best be done by the numbers per Eismann and/or Margulis.
But my favorite numbers for a model are 36-22-36.
Tom Nelson wrote:
Skin tones vary a lot even among racial groups. Here are a few notes I’ve made about caucasian skin. They relate to different images whose skin seemed good, so the individual notes differ.
HSB brightness of 77% is equivalent to a medium suntan. Look for around H=23° S=40% B=77%. Read a part of the face (I like the forehead) which is neither a shiny highlight nor in shadow.
In HSB, try a highlight brightness value of B=78%, shadow B= 27% H=22° S=40% B=77% is equivalent to R=199 G=152 B=119
A model in makeup had HSB ranges of:
H=18-25
S=26-45
B=71-89
Color guru Dan Margulis, in a rare excursion from his CMYK aerie, says: Caucasian targets are around:
R=150
G=50
Y=90
[You’d have to read the yellow by choosing CMYK as well as RGB in the Info palette]
Tom Nelson
Tom Nelson Photography