From Outwar Wiki
Glows are used to designate and group special items from regular diamond city drops from mobs.
The glow itself has no bearing on the stats of an item. Items always have the same glow throughout the game, i.e. a Government belt always has a green glow.
Blue: This glow is given to the common crew set raid drops, i.e. Turtle Blades
Blue-Green: This glow is given to all drops in bacaba including the Celestial Set
Red: This glow is given to the uncommon crew set raid drops, i.e. Turtle Shield
Green: This is given to sets of any type, i.e. dissimulation through oblivion
White: This is given to the "Gods" type of items, dropped from guardian raids, i.e. Great Blade of Ferocity
Orange: This is given to the Stoneraven type of items or items which are really good.
Purple: This is given to the equipment dropped from the server guardian raids (Blackhand, Sandman, Chancellor Fangore) i.e. Blackhand (the weapon)