Step 1:
Basecoat all of the skin with a nice desaturated green. I currently use army painters army green, but this works fine with an olive green as well (I’m considering getting some other greens in order to vary the skin tone on my orcs).
You may notice that I use xenithal priming – this is entirely optional, I do it because I feel it makes it easier to see details, not because it has any effect on the colours themselves.
Step 2:
Now I give the skin two thinned down highlights with army painter camo green – This can easily be replaced by adding one part of an ivory colour to three parts of the base colour. I generally thin colours with liquitex matte medium and a bit of water, but really you could just use water.
Step three:
My final highlight is made by adding some more ivory to the skin tone – this time I used army painter drake tooth, but any ivory colour works fine. In this case I used 2 parts camo green to one part drake tooth.
Step four:
Next I glaze some additional colours onto the skin – generally I use a light flesh colour and magenta. I heavily recommend using some medium for this step, but water does work too. On characters I’ll often paint the whole thing using shades and glazes, but that takes too much time on rank and file figures – it is however great for adding some nice colour without changing the values too much.
In these cases I used three layers of each glaze, with a third on this specific model for the wound on his head. I add magenta to places with thin skin or in deep recesses, as well as any visible blood vessels (I guess my orcs have reddish or magenta blood), while I add the flesh tone to extremities that might have thick or worn skin, such as brows, chin, elbows and knees, knuckles and the palms of hands.