Origin of Phrases - S
Show your true colors
Meaning: To reveal your true intentions, personality, or behaviors.
Example: Everyone is on best behavior on the first date, but soon enough you will show your true colors.
Origin: Color(s) has numerous meanings. An early use of the word is flag, pennant, or badge.
Early warships often carried flags from many nations on board in order to elude or deceive the enemy. The rules of civilized warfare called for all ships to hoist their true national ensigns before firing a shot.
Someone who finally "shows his true colors" is acting like a warship which hails another ship flying one flag, but then hoisted their own when they got in firing range.