Four colours were used: Red, Green, Blue and Black.

Somewhat inspired by Helm's Spartan piece I started experimenting with RGB pallete - this is the result of one of such experiments. I'm still trying to work out the best method of workflow for this type of images. This one is too "vectory" for my liking.

I used that photo for reference (warning - contains nudity): http://mjranum-stock.deviantart.com/art/NightFae-1-155550979?q=gallery%3Amjranum-stock%2F4158526&qo=6 My first idea wast to create whole character but I got stuck in trying out different methods of work so I settled for the head in the end.

EDIT>> This is the actual head image I was working with, tones and contrast adjusted so that the head is actually visible, plus some filters added to the image to block out the colours better: http://ixolite.info/grafika/RGB-head-ref.jpg  <<END OF EDIT

I used the reference photo to trace out the basic shapes (hood, and face), filled them with base "colour" and started adding layers of shadows and highlights on top of that. After that I carried on with some finishing touches that didn't really make a difference in the end.

The way the "colours" are composed didn't really give me any flexibility in mixing them :/ But I have some other ideas about laying out the pixels to try out.