Gold is not full of red, and no one is perfect
It comes from Song Dai Fugu's "Jixing": "Gold is not full of color, but white jade is slightly flawed. Asking for help is not prepared, and I wish the old gentleman's family. "
It's also a metaphor that you can't ask a person not to have any shortcomings and mistakes.
There are no perfect people in the world, and there is no absolute deficit in gold.