While I don't have a Forgeworld book telling me the exact colors they used I can tell you how I would paint something similar. Let's take a look:
Silver Metal: They have used a lot of stippling and sponging to create a very weathered and aged metal effect.
Base: Leadbelcher
Wash: Diluted Nuln Oil 1:1 with Lahmian Medium in recesses Now the interesting part: Using
sponging technique apply dark grey/black to the outside of the panel lines. Using light grey drybrush/stipple middle of panels.
Stipple the panels uniformly with leadbelcher to create broken/mottled pattern within the black/grey.
Highlight: Drybrush and edge highlight all the edges with ironbreaker or similar silver. Add random silver streaks to taste within the darker areas.
Bronze areas:
Base: Runelord Brass all over.
Wash: Diluted Agrax earth shade all over.
Stipple with Dryad Bark on edges of bronze. (Very conservatively)
Stipple/sponge with Runelord brass to create mottled pattern.
Stipple/sponge on Sycorax Bronze.
Edge highlight with Silver.
Orange Orbs:
Base: Jokaero Orange,
Layer Troll Slayer Orange,
very top highlight with yriel yellow. (Blend each color into the previous one, painting a smaller and smaller area)
Markings:
Wash undiluted Serapin Sepia into markings.
Edge highlight with Ushabti Bone. Give
finer edge highlight with Screaming skull at very corners.
I hope this helps. Cheers!
These are some of my works in case you wanted to gage if I have any idea what i'm talking about: