The Raiders use a brown and green camouflage pattern, which they change only when it clashes drastically with the terrain in which they are currently operating.
Per FM: Merc (revised), page 92.
Spector, FM: Mercenaries (plate 15)
Atlas, CM: Mercenaries (p 111)
Their insignia is a horned animal skull on a white-rimmed blue circle. Per FM:Mercenaries Revised, page 92.