Use a suitable camo, though they sometimes fail to update it in time, keeping an old paint scheme even though it's no longer relevant. They however always display the white and black highlights that are the trademark of the unit.
Canonized by Foxbat on 3/29/2008.
Ace's Darwin's Whipits
April Fool's Brigade
The Angels use a pristine white paint scheme with gold trim.
Per FM: Merc (revised), page 40
Per FM: Merc (revised), page 41
Barber's Marauder IIs
The Battle Corps
Tan with blue highlights. A 'Mech's left leg, fighter's left wing, vehicle's left flank or Battle Armor's or Protomech's left side is customized by each warrior, most of which choose to display schemes of previous allegiances.