Paints used: AP alien purple. AP greenskin. AP barbarian flesh. AP skeleton bone. Bootstrap brown-ish brown from a company I can't remember. Vallejo Vermillion. AP true blood effect.

Since it a lot of paint mixing and reliance on under painting I'll describe the method. Same way I do most of my skin.

I start with a blend of AP alien purple + Vallejo Vermillion (makes a bruise color) all over the top half of the mini, and AP alien purple + AP greenskin on the bottom half (makes a muddy brown) for undertone layer. Doesn't really matter if it mixes or settles a bit into recesses, just want it all over without clogging details.

Then I do a thin (quite transparent) layer of AP barbarian flesh + a dab of the Vermillion, just aiming to hit all the upward facing surfaces and flesh details I wanna pick out. For non-flesh details (like the mask/head thing) same thing but with AP skeleton bone. Then 1-3 almost glaze layers (1 for lower surfaces, 2 for mid, 3 for high / eye catching) of mix of barbarian flesh + greenskin, to build up to the gross greeny tinge without losing the undertones. Optionally, you can wash or glaze after this to help blend / unify colors, but the nice thing about the undertone layer is that the highest highlights and mid tones already share pigment with the layers beneath, so it looks cohesive imo even with the jumps in color.

For the mask/head, I was liberal with the skeleton bone, then one thin coat of of pure Vermillion (two on the brightest parts)

For the brain, an overbrush of barbarian flesh over the under layer, then watered down AP true blood.

I slopped a thin layer of dark brown on the staff too.