I would have said reds first, followed by 2nd yellows, then first yellows. As has been mentioned, get the worst idiots off the pitch ASAP, then deal with the morons, thank the sensible ones for their patience and get on with the game.
Thankfully I've never had to deal with anything too serious, but was AR for a ref who, once all had died down, called the two captains over, said, "Right, I want all your (home) lads over there to my left, and all your (away) lads over there to my right. I will tell you who I want to speak to and you bring them over to me, one at a time OK?"
"Yes ref"
He then went through the list (two reds, one 2nd yellow and three yellows) and the captains had to walk back and forth, bringing each player to us.
Felt like an old school headmaster, but it worked.