As promised, I thought I would post my recipe for Green Martian skin. Here are some pictures of Tars Tarkas from my LPL IV Round 10 entry:
Tars was done with elements of the Foundry Moss Green triad over a black undercoat. I started with Foundry Moss Green 29A, then washed that lightly with the Citadel Gnarlock Green wash, thinned 1-3 with water. Then I applied a 50/50 mix of the Foundry Moss Green Shade (29A) and the Foundry Moss Green Mid-tone (29B). Then I highlighted with the Foundry Moss Green Mid-Tone by itself. The Foundry Moss Green gets very yellow as you go up through the highlights and I didn't want to compromise Tar Tarkas' green color, so I stopped there. His teeth and tusks were done with the Foundry Bone triad and his tongue with the Foundry Purple shade and mid-tone colors. I did the pupils of his large eyes in black with a tiny white fleck of highlight in the center of the pupil (although Burroughs specifies that Green Martian's pupils are red).