>>7665007You start with the base/undertone colour which can be hard to see without practice, let alone from imagination.
Getting the base colour correctly can be hard to do since you're training your eyes to ignore all lights and (sometimes) shadows from objects.
You can see it more clearly when you compare the OP's hair and skirt since they both use the same base colour. With the hair, you'll immediately notice how flat it looks with zero depth. While the skirt takes advantage of light shadows to build a rough shape and then adding light values to sculpt it more clearly, and finally going back with the shadows to refine it's shape.
You gotta do a lot of practice pieces before you'll get anything that looks amateurish and not like utter vomit garbage though
And when you do, you then gotta go back and practice different colouring techniques to emulate different textures and colour varieties