The segmentation of the universe into four sectors, each gouverned by one race, is crumbling. Peace is not an option any longer – all you can decide is which path of war to follow.
Races following the path ironically called 'peace' (represented by the colour green) attempt to expand their empire by settling on as many planets as possible. These colonies are then built up through investment into industry, defense, education and so on. This brings in tax money and after some time, these planets will be able to defend themselves against attacks quite well.