Any really! Yellows and oranges can be a bit hard on the eyes though, cool colors will probably do you better
Pick a dark one for lineart, a lighter but still dark one for the bg, then the lightest one for filling in the lineart
Shade and light however you’d like and yeah,,, that’s how I do it
I was the one who started it, and is like you to know that youre very special to me and that I care about you even if I'm mad, its difficult to deal with emotions like that since I'm not too used to it, maybe one day I'll learn