I think the best way to understand when it comes to utilizing value and color is to actually get out paints and do them yourself. Somehow mixing and laying them down commits to memory these principles in a way entirely different than simply reading them in a book. Does this make me old-fashioned? I don't know. Most art pieces I look at digitally seem to lack efficient contrast, especially when it comes to the human figure. So I like revisiting value and color to remind myself of these basic things.
Of all the exercises, I think I would choose to do this one a hundred times.
And something about doing up the color yourself... I just love it.
Some harmonies and a stuck-on dissonance. I need to work with dissonance more often.