I don't doubt that every unit is different, all kinds of SOP's vary. However, the units I trained for CQB in, once the room was clear you were back at the low ready, on red with your IR off unless using the flood to look at something. However whenever going through a door (on a raid) we were weapons in firing position, and at least the 1 and 2 man went in black.. We used our IR a lot in training to develop awareness of flagging your buddy..
Lots of ways to skin a cat though, some of us went in to the corners, some units "strong wall" a room I'm sure others do other things. All of them work, as well as everyone is on the same sheet of music.