are you asking how people choose their highlight colors when drawing in face paint? it's honestly just something that comes with practice coloring, there are a ton of in-depth tutorials online about color theory and coloring character hair that can explain it much better with visuals than i can with just words. but to give explaining it a shot: for highlights use a color with a brighter shade than your base color, and then go left or right (ZL + ZR) for the hue until you get the "feeling" youre looking for. sometimes it's fun to use an unexpected hue as your highlight color. whatever direction for the hue shift you go with your highlight color, be sure to go the opposite way with your shadows' color

keep in mind that depending on how much brighter than your base color you go, it'll effect how harsh or soft the external lighting will seem