Hi, Beth.
I apply both the rule I quoted as well as the 'warm light source/cool shadow and vice versa theory'. I think that what you are confused with is that there is a subtle difference when you talk about hue. For example, you have a subject bathing in warm light, so you decide that the colour 'yellow' is the colour that you want. Once that is identified, you have decided what version of the yellow that you want. Is it a yellow with a cool hue version, or a warm version?
In a painting, the part that is closer to the viewer would be painted with a warmer version, and vice versa. Cooler colours/hues recede and warmer ones come forward. It is a like an illusion that you want to give to the viewer. You have to also see which is more of a dominant colour. So, for example, the recent painting that you posted, his left shoulder blade is farther, it should have a cooler version of the ochre (or a cooler colour) that you have chosen for the part that is closer to the viewer. Same thing with his nose and left side of his face. The nose was painted with a much cooler colour (which has the illusion of receding), while his shadow on the left cheek (painted with a warmer red colour), which appears to come forward, etc.. His left hand is painted in a dominant yellow
colour, when it is the farthest object in the painting. I would use a different colour for that hand (some cooler olive ochre, light blue highlights with cooler brown or violet for the shadow parts).
For your reference, you can look up
"Capturing Light and Color with Pastel", by Doug Dawson (my favourite book). It is out of print so I don't know where you can buy it now, but I am sure any good library would have it. It is an excellent book and I refer to it from time to time. In the book, he has good sections on colour theory, compostion, light and shadow and how to paint certain (difficult) subjects.
Another book that you can look up is The Fine Arts Series "Theory and Practice, Basic Principles & Language of Fine Art". I like it because it teaches and explains colour theory, composition and lights and shadows in a 'scientific' manner. It also explains to you 'why' things are in certain ways. And once you understand 'why' things work (the basic principles) you can apply or manipulate it better as you paint.
Mai