I'd say base abaddon black, maybe a druchii violet all around shade, then precise highlights with
~screamer pink / xereus purple, genestealer purple
Most extreme highlights should be pallid wych flesh (probably with a dot or genestealer or xereus purple), regarding the color scheme.
Bronze : retributor gold, agrax earthshade, hasnut copper, highlights liberator gold
Scorched Skin : cadian fleshtone, druchii violet, kislev flesh (probably bleached bone for 2nd from left)
Viasages skin : cadian > kislev > druchii > pallid > mix w white scar
Eyes : white scar, green ink (might use warpstone glow)
Edit : Add the picture, in cas it gets 404'd (thinking of you, futur guys)
Hint : Most of small details are shaded with druchii violet to link the whole, except eyes & hair, for contrast and focal points
Hint : Some highlights might contain some deep red (mephiston/evil sunz) to add variety