Looking like a lot of grey tones were used, the more cool variety like the colours that have the hint of blue for the armour/would be gold parts.
I can the green is blended into a brown, looking a a light green with a recess shade of a brown. Looks more like a darker shade of Dryad Bark.
Or possibly it's a brown paint for the basecoat and then carefully drybrushed/highlights with greens for the scales and a bit of wetblending for the face.
As for the colours themselves, for the browns I can see Dryad Bark with a layer of Gorthor Brown.
Greens, Waagh Flesh base coat, Moot Green and Skarsnik Green for the layer.
Agrax Earthshade could be used for the brown but it's hard to tell. I can see a brown used on the stone area
This is going by my own collection of colours that I have so far as looking at GW's website doesn't give a clear idea on how colours look. There is other brands of paint out there but I don't know much about matching the colours in those areas.
Hope this is helpful.