The Long Striders’ colors are midnight blue trimmed with red, white and silver.
Per Mercenaries Supplemental, page 33.
Other references:
War Dog, Mercenaries Supplemental (color plates)
Grasshopper, CM: Mercenaries (p 109)
Gregg’s Long Striders’ insignia is a giant lumberjack walking over the face of a planet with an axe over his shoulder. Per FM: Mercenaries Supplemental, page 33.