Here's what I did to get my dudes looking like this:
Armor:
- Prime with Army Painter's Skeleton Bone spray, then touch up any areas missed with their Skeleton Bone bottled paint
- Wash whole model Agrax Earthshade
- Paint model again with Skeleton Bone, but leaving the recesses untouched
- Highlight with
GW Screaming Skull, with Ceramite White (or any pure white really) for the extreme edges
Green:
- Paint with Caliban Green/Army Painter's Angel Green. Over the Bone basecoat, the thinner green paint actually gathers in the recesses, effectively washing the area for you. If it doesn't, a green wash will do the trick.
- Highlight with Warboss Green, with a Skarsnik Green extreme edge
Red:
- Khorne red, with an Agrax Earthshade Wash
- Bring back up to Khorne red, leaving the recesses untouched
- Highlight with Mephiston Red, with Squig Orange (
IIRC) for extreme edges
- Use these same colors for eye lenses, with a dot of white in the far edges
Metal:
- Leadbelcher washed with Nuln Oil
- Drybrush/highlight with Runefang Steel
Gold:
- Balthasar Gold
- Gehenna's Gold, leaving Balthasar Gold near the recesses
- Auric Armor Gold highlight