The green areas represent virgin Neutral Areas as-yet untouched by battle-tainted weapons.
Neutral Areas are the open and free, lush and natural, resource-rich and high-potential lands that form the object of unending territorial dispute among the four civilizations in Imperial Warfare. Each server starts with a great proportion of its land constituting Neutral Area, and the endgame comes ever nearer with each Civilization's occupation of previously neutral regions.
Once Neutral Areas have all been taken, then the game starts to get really heated, as every bit of contested land has already belonged to at least one Empire. Let the wars begin.
Neutral Areas are occupied through Neutral Area War declarations on World Wonders within the Area; these declarations may be initiated only by the leaders of Guilds with more than 30 members, 100,000 Gold, and 10,000 Fame. Once a Neutral Area is taken by a Guild, Guild members with at least 10,000 Fame may build Camps within that Area.