If you mean the way he is closing one eye, then that is called a 'wink' (close and open one eye quickly, typically to indicate that something is a joke or a secret or as a signal of affection or greeting.)
'Wink' is both a verb and a noun. So you can say "The man is winking at the woman."
'Collusion' doesn't really work in this context. It's a more formal thing. For example "The law was never very effective at stopping organised crime because the police were in collusion with the Mafia."