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I don't know whether you start colouring with the shading or with the base colour, because pretty much everyone starts differently. So I'll just tell you how I do it.

Usually when I colour in pencil crayon I start with a light walnut type of colour. Just any light brown, not too dark. I use this as the shading. Then I'll find a peachy colour and colour over the shading to blend it, and colour everywhere on the skin except where the highlights will be. Next, I find an eggshell sort of colour, something lighter than the base skintone, almost white. Use this to cover everything that is skin, blending what's already there and colouring in the highlights.

Of course if you have a limited range of colours it would be easier to just shade with brown and start dark, and end lighter, then go over with peach.

Some people shade with pink instead of brown. If you want a colder atmosphere shade with greys and blues.

Also, that was assuming that your drawing is Caucasian or Asian. If you're going for African the same rules really apply, just use darker colours.