sail under false colours

sail under false colours

  (British & Australian) also sail under false colors (American & Australian)
to pretend to be something that you are not in order to deceive people
Usage notes: If a ship sails under false colours, it uses the flag of another country in order to deceive people.
Lewis was sailing under false colours - he never told her he was a journalist.
See also: colour, false, sail
References in classic literature ?
You sail under false colours from beginning to end,' he said.