The Grave Walkers: All Good Things
The Grave Walkers paint their `Mechs forest green with sea green highlights.
Per Mercenaries Supplemental, page 32.
Other references:
Dasher, Mercenaries Supplemental (color plates)
Awesome, CM: Mercenaries (p 108)
Their insignia is a skull on a tombstone. Per FM: Mercenaries Supplemental, page 32.