From YPPedia
Greeter-only commands

The /duty command allows greeters to toggle their duty status. While off-duty, the greeter appears as yellow to all players, does not appear on the /who list for the greeters on the island, and can not receive any tells from greenies using the Talk to a Greeter button. If a player is not eligible to be a greeter, they will be unable to use this command.

The /duty command also generates a "You are now on/off duty" message, to inform players of their current greeter status.

/duty (/du)

Historical notes