I call them "randoms" but I don't speak to them, ever.
White, Yellow, Blue, Green,
I call them idiots. I only play in a party because without a team of at least 3 the win rarely comes.
We call them Randoms.. Or Green Guy.. I personally use Randoms though... Or RanDumbs because most of them are idiots that have no clue how to play like a team.. Call outs etc...
Greenies, thought everyone did.
I normally shout out.....you fucking idiot!
Etiquette would be to call them whatever their gamertag is and not be rude.