In naval parlance a ship "sails under the colors" of her nation, meaning that she flies the flag of her country of origin. During the years when vessels literally sailed, a ship's colors flying from the topmast were the first sign of her presence to show over the horizon. Pirates and such would often fly the colors of a merchant-ship or convoy for which they were lying in wait in order to disarm the suspicions of their intended victims and get closer than might otherwise be possible. In times of war, the well-equipped raider, corvette, frigate, etc., had several sets of her enemy's colors in order to mislead an opposite number--either to come closer to one she thought she could take, or to elude a larger opponent in order to get out of harm's way. But NO captain of any honor at all went into battle under false colors. He would ALWAYS haul down his false colors and run up the true before engaging. Thus the term "false colors" today refers to intentional deception of one kind or another, and "true colors" indicates straightforwardness or honesty in some regard..