A Rocky Start
The Widowmakers paint their machines black, with a red spider-like mask (rumored to have changed from gold due to Major Wannamaker's resentment towards the Dragoons, and the possibility of a feud) painted over the faces of the unit's BattleMechs and the fighters' engine cowlings.
Per Mercenaries Supplemental, page 64.
Axman, Mercenaries Supplemental (color plates)
A red spider-like mask is their insignia. Per FM: Mercenaries Supplemental, page 64.