It really depends on the setting and type of white I want to depict, but the standard is doing the shadows in blues mixed with light grey and hints of peach. The warmth of the peach coupled with the cold blue makes the white pop. If I want a more muddy or warm white I go with greys and purples, warmer colors generally. What's interesting about white is it reflects all the colors, so if you have something red near it you can add a bit of red to the white that's near the object, and when you're showing a character bathed in a color the white will fully take on that color. Same with setting. I haven't drawn characters with white hair in a Hot Minute, but when I have something white during an evening setting I'll make it pinkish or kinda yellow depending on how late it is. If it's nighttime I'll make it a solid light blue.
White is fun, you can do a lot with it.
Edit!: This sketch is from 2011, but gives the gist of what I mean with the standard shading.