Academic question
 

I know that one is supposed to paint what is in front of one's eyes, however from the academic point of view I have the following question:

In the area where the light meets the shadow (known as the half tone), there is a change of color temperature and the body color becomes more saturated. My question is as follows:

In what part of the half tone occurs the more intense color?

a) in the first half of the halftone?
b) in the second half of the halfone?
c) in the entire halftone area?
d) What will be the temperature of this area of intense color (cool or warm?).

Thank you, and to show that I am not only interested in theory I will scan soon some portraits I have done.

Depends
 

There are no pat answers. Every question you ask will depend upon the subject, the light (temp, direction, intensity) and many other things. If you "paint what's in front of you" you'll need only trust "what's in front of you" and will not need theories. That's the beauty of working from life.