Why blue and red team?

[Tempered]

Red and blue have always been used to represent two opposing forces. When you have players on both sides, you can't really say "Red is always the enemy" now can you?

Besides, the game is setup so as to allow any number of nations to be at war, either in a historical or fictional context. What if I wanted to make a scenario where Canada invades the U.S. Who would you call the "allies" and the "axis" then?