Okay, use a wrench on the green button.
Somewhere on there is a line that defines the code, I think. Otherwise, admin-orb into the room and behind the door is a couple buttons (not the back side of the ones on the front), said buttons set the code.
Simply say a numerical code, and then activate the button.
EDIT:I'VE GOT IT
I finally got blockland open. There is no code set by default.
Simply touch the door (assuming your SA), say the numerical code, click the rainbow brick, then go back out, type in the code, and hit the green button.