meow_

Maybe I wasn't clear enough, my bad! I basically mean taking painting principles and applying them in-game. Just grabbed an image from the net to show what I mean - as you can see on the left you get muddy-looking tones when a skin tone is simply darkened (APB equivalent adding semi-transparent black or grey) vs. when a hue differential is added between highlights, midtones and shadows on the right giving more life / depth (in APB, making the semi-transparent layer(s) slightly saturated in a shifted hue): I could hop in-game to make an example if you want but I hope the idea comes across from this. At the end of the day it's all down to personal preference, though, of course.

Nice simple tutorial! The only thing I would add is that shadows on skin can look more realistic if they have a little saturation rather than being straight grey / black. For example, on light skin tones I usually use a dull-ish brown (with a change in hue to avoid a muddy finish), but really it's just another one of those things that you get the best result with if you play around a little.