Right, here's what i did.
Pic 1 is the pattern for it drawn over the basecoat of "Bleached Bone".
Pic 2 is where i panic big-time - going over the pencil with a band of dark grey.
Pic 3 is me feeling a little bit better as i fill in the inside areas with a dark brown.
Pic 4 is me feeling even better with Vallejo "Desert Yellow" mottled over the brown, a lighter grey inside the dark, and a wash of "Scorched Brown" over everything.