GreatKhanArtist if you want so, I'd be pleased
mr. dude I don't consider myself an authority in painting OSL, but can give you a few tips:
1. I have not acknowledged consciously any "colour theory"
2. I'm improving my skills using YouTube (there is plenty of tutorials how to paint OSL)
3. Sauron was preshaded using airbrush - dark blue in the shadows, yellow/white in the highlights. Airbrushing with yellow was a mistake, because midtone between highlights and shadows was green and i have to cover it using blue/red/orange/yellow glazes.
I've chosen position where the photo will be taken (and everyone will look at him from that position) and sketched highlights.
The rest of the work is to create smooth transition with glazes from blue-red-orange-yellow-white. Top highlights were painted in near-white colours, pure white was used to create "blinks" (i dont know if it is the proper word for it), small dots in the most exposed areas to enhance contrast.
I wish it would be helpful for you