false colors

The guise of false pretenses, so as to deceive someone or to hide one's true nature or intentions. (An allusion to the identifying flags of a ship, and so usually used in the phrase "sail under false colors.") Primarily heard in US. Tim thought he could just put on fancy clothes and rub elbows with the upper crust that Janet's family socialized with, but everyone at the party knew he was sailing under false colors. I don't want to be accused of flying under false colors, so let me say straight away that I'm being paid to give a review of this product today.

Pretense, misrepresentation, or hypocrisy; deceptive statements or actions. For example, She's sailing under false colors-she claims to be a Republican, but endorses Democratic legislation . This term alludes to the practice of pirate ships sailing under false colors-that is, running a particular flag specifically to lure another vessel close enough to be captured. [Late 1600s]

To behave deceptively; to misrepresent oneself deliberately. The term comes from maritime piracy, rampant from ancient times until about 1825 in Atlantic and Mediterranean waters and still existing in parts of the Pacific. In order to deceive their prey, pirates would run a “friendly flag”—that is, “false colors”—to lure their victims close enough so that they could easily be captured. The term began to be used figuratively in the late seventeenth century. Robert Louis Stevenson used it in St. Ives (1897): “I had so much wisdom as to sail under false colours in this foolish jaunt of mine.”