Oh, forgot to mention...
The colours really don't mean much, they're just there to tell the difference between everybody's armies on the map. Red is the person who started the game, then the second, third, fourth, etc. each have their own separate colour, whther it be green, dark blue, yellow, pink, or light blue.
If one continent is gray, that means its controlled by a neutral player. That means it was either the leftover territory when the armies were handed out in the beginning of the game, or it was previously owned by someone who had surrendered/been a deadbeat.
