There is no Green Galaxy. There is Green Crystal only for a quest and only to recharge OTHER crystals.
There is a RED Stargate, BLUE Stargate, YELLOW Stargate, and BLACK/GRAY Stargate.
RED: Milky Way
BLUE: Pegasus
YELLOW: Ida
BLACK: Uhhh...Don't know and don't care.
I don't know if SGA still uses Green Crystals for Ida Galaxy when they're technically suppose to be yellow but meh.