Color theory is MY THANG.
So, color is great, because you don't have to use the "right" colors to convey something, color can be used to trick the eye. I learned a lot of my color theory while doing pixel art, limited color pallets force you to get creative. Am I correct in assuming you're familiar with the basics like the color wheel? https://www.colormatters.com/color-and-design/basic-color-theory (<-Randomly grabbed reference from google)
Once you know that stuff, it can still be hard to decide what colors go where, so Saeyra is correct that references are great when you're learning... both photos and other drawings. Use the eyedropper tool around a piece of art/photo and really pay attention. Colors that read as warm browns to the naked eye end up being more like pale blues or greys.
My general rule for coloring anything is that things that are closer to the viewer (or highlights) should be warmer and more saturated, things that are further away (or shadows) should be cool and less saturated. AND because every rule in art is meant to be bent or broken, it can work the other way around, too, its more the contrast that makes everything come together.
http://humanae.tumblr.com/ is a tumblr dedicated to showing diversity in people, and they use pantone color to show the "average" of their skin color. Its also pretty great for referencing diverse facial features.
Ok, this reply is pretty rambly, but there is a tutorial I dug up that helped me a lot in the past. They're a bit better with words than I am, and they've got graphical representations to convey it :D http://www.floobynooby.com/ICG/artvalues.html I hope these things are useful!
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Always ping me please. 