a white lie

(little) white lie

A lie thought to be insignificant and justified, especially one told to avoid hurting someone's feelings or giving offense. I try to be honest most of the time, but I do tell white lies when I'm worried about upsetting people. A: "Do you actually like her new haircut?" B: "Of course not, but I couldn't tell her that, so I told a little white lie instead."
See also: lie, white
Farlex Dictionary of Idioms.

a white lie

If you tell a white lie, you say something which is untrue, often in order to protect someone or to avoid upsetting someone. I said she looked nice, thinking it kinder to tell a white lie. I believe that this is a case where a little white lie is really more appropriate than the truth.
See also: lie, white
Collins COBUILD Idioms Dictionary, 3rd ed.

a white ˈlie

a small or harmless lie that you tell to avoid hurting somebody: When she asked me if I liked her new dress I had to tell a white lie. I thought it looked awful, but I couldn’t say so!
See also: lie, white
Farlex Partner Idioms Dictionary

white lie, a

A fib told out of politeness, to spare feelings, or for a similar reason. The term is intended to distinguish between such a fib and a black lie, considered heinous dishonesty. A 1741 issue of Gentleman’s Magazine stated, “A certain Lady of the highest Quality . . . made a judicious distinction between a white Lie and a black Lie. A white Lie is That which is not intended to injure any Body in his Fortune, Interest, or Reputation, but only to gratify a garrulous Disposition, and the Itch of amusing People by telling them wonderful Stories.” However, warned William Paley in Moral Philosophy (1785), “White lies always introduce others of a darker complexion.”
See also: white
The Dictionary of Clichés by Christine Ammer
See also:
  • (little) white lie
  • little white lie
  • not the half of
  • not the half of it/(something)
  • nothing burger
  • one or two
  • loose change
  • don't spend it all in one place
  • What do you want, a medal?
  • mean nothing to (one)