Grey = Worthless - Can be won by attacking Faction Camp Generals - Disenhance to gain bronze to use for gaining Enhanced Steal and Faction Quests.
Green = Good - Best practice is to complete your Grand Melee duels daily - 6 generals a week - 3 generals a day - 10 duels ea. - Total of 30 challenges a week per general and you will qualify for Fame points. Exchange Fame Points for valuable equipment.
Blue = Better - Can be won in the Grand Melee event also.
Pink = Getting Good now - Can be won in the Grand Melee, but it's rare - Best practice is to buy Ares chests and get it that way.
Purple = GREAT! - Must be gained through a TKO related Special Event or found inside of a Ares Chest.
Red = THE GRAND DADDY OF THEM ALL! - Only one way to get red equipment - TKO Special Event giving it away.