Reds are taught from a very early age to “never hit greens.” Greens, however, are not taught the same thing when it came to them hitting reds. In fact, society thought it was funny or deserved for a green to hit a red. Reds are taught that protecting greens from harm is the sign of a “Real Red.” As such, only reds are drafted in times of war.
A society like the one in this universe would seem primitive and racist, some would say savage, compared to home from the point of view of most people. Remember though, that all we changed were two terms.