Plain-Color Voxel Game Lighting

As a practice, I am trying to emulate visuals of Cube World (cannot be played anymore).

I currently have Color[,,] (3D Array) to Mesh converted which separates colors into submeshes and assigns own material for each color (instead of having them in 1. "Simple Custom" is assign color and use "Lambert" lighting (with "VertexLit" as fallback).

For the ground (terrain), I will settle on texture projecting its color from top (whole block face same color).
Characters are different. I want them to be only few colors. For example hair from screenshot below would be only 1 color and shades should be made by lighting (angle to sun, shadows).

Result lighting should be light on surface but darker indoors and dark in dungeons or under ground.

How to make the desired effect? Without implementing whole custom lighting.

Inspiration: Screenshots found at Cube World Game Wiki