Well SCV has been trying to distance themselves from 2005 sence july of 2005. Some of my teachers are SCV alumni and are active in corps poiltics and all that jazz. SCV Alumni almost pulled the corps because they acted in a non SCV manor (picking fights with BD and stupid crap like that). If you watched there Memorial day weekend podcast, it was all about 2004 SCV. Rick was fired from corps director and fired about all the rest of the staff too. The reason why they brought back the white pants in the first place was Rick trying to bring back the "golden years" of SCV (the 80s for the most part). Thats why they did the remake of the Russian show, and why they brough in the white pants.
ok so now here is what I belive
They changed into the green pants because it gets back to the 2004 SCV we all know and love. The alumni was proably at falut for the change in pants, claming that white pants was for the 80s and that it's not the 80's for vanguard anymore. Thats why the 2005 uniform look almost exactly like the 80's uniform. SCV proably didnt wanna dish out the money for a brand new top desine too, so to change the look of SCV quick and without costing them to much money. They just changed the pants.