Wvw Color
Each week, the servers are matched up with one another based on their points at the end of the week (the reset date being Fridays). Typically the top team in a threesome is assigned to green, the second blue, and the third red.
If you are constantly on the red side, then that suggests that your serve has always been last in its matchups. Changing this would require earning enough points to move up in ranking or the system to shuffle your server out into another matchup where it might be placed in/earn a different spot in the new threesome.
a general starting point to read more: http://wiki.guildwars2.com/wiki/World_versus_World