Today's idiom is " a white lie ".
This means a small lie that doesn't hurt anyone.
Example 1
A. My Mom has had a face lift, but she tells everyone it's natural.
B. Well, that's alright. It doesn't hurt anyone. It's just a little white lie .
Example 2
I told my girlfriend I liked her haircut, but actually I didn't. I had to tell a white lie or she would have got angry.
https://www.merriam-webster.com/dictionary/white%20lie