After blocking in the colours I went back in and started to develop the colours towards their real hues, adding more subtlety to the general colours that went in first. I also put in more darks, to give form to the subjects, and because I want the background colours there when I start layering on top (in the hair, for instance).
It's progressing fairly well, though I seem to have switched tactics halfway through, because it's considerably lighter on the right hand side. Partially this is because I'm giving the girl a slightly different skin tone to differentiate the two, but it's supposed to be more subtle than this. That, of course, comes with the eventual layers. I'd rather have things much starker than necessary to begin with than try to add them in the end. Also, I always work from left to right because I'm right handed and don't want to smudge what I've done before, but sometimes this backfires a little if I change things, or leave off before the entire layer is finished, and this is the result. Oh well! There's lots left to do, I'll fix it eventually.