ive found that, living in a more or less all-white region there are typically white-whites, yellow whites, pink whites, and warm (orange/brown) whites, and the differences are very, very easy to spot. everyone though has a variety of tones on and under the skin that make for a huge amount of variation. as highlighting is concerned, the more light is on something, the more 'true' it will be to what its natural saturation is, but everything can be distorted, especially if the light is not white. in terms of patterns in this, saturation in my experience neither heightens nor lessens based on any real set rules that ive been able to discern. low-sat colors (in white light) can gain saturation in shadows, and high-sat colors (in white light) can lose saturation in shadows, its all tricks of the light to me. anyone can set me straight if they like
thought: perhaps, since shadow hues move towards the hue of the air (does this fall under atmospheric perspective? i just know it as a foundation of color theory), the saturation values in shadows also becomes that of the light reflecting off the air between the viewer and what is seen, therefor able to be more saturated or less saturated than when viewed in normal white light?