I use dithering a lot to blend colors. ' ___ '
Like helm said in the ramblethread ... ? He said it somewhere anyways: "Dithering is at its best when not noticeable"
Good color blend dithering adds colors that trick the eyes. One of the best ways is to dither between low-contrast colors, for example, or to dither somewhere where the brain notices the edges of two color clusters, to make it less noticeable. Dithering where the brain doesn't 'catch' the bands, is just creating noise and unnecessary complexity.
Aaand that's what I'd like to tell you right now: Whether you want to use dithering or not in the end, THIS is not the time. You need as much clarity as possibly possible when trying to place lighting and shadow in a way to sculpt a face that has likeness to a piece of reference - you don't have room for noise and complexity! Sculpt your image with color clusters, making it work with that, then, if you feel like it, dither the places where the bands/clusters collide.
That's all. Oh and yes.
SCOLD! Your first one was better, rendering-wise. Take your new colors and new shapes and apply it upon the old one, sans the dithering. And do add the eyes, too, they're important reference points anyway.
