Meaning of the word "the fox may grow grey, but never good" in English

What does "the fox may grow grey, but never good" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

the fox may grow grey, but never good

US /ðə fɑks meɪ ɡroʊ ɡreɪ, bʌt ˈnɛvər ɡʊd/
UK /ðə fɒks meɪ ɡrəʊ ɡreɪ, bʌt ˈnɛvə ɡʊd/
"the fox may grow grey, but never good" picture

Idiom

a person's character or nature does not change even as they get older; used to suggest that a wicked person remains wicked

Example:
He claims to have changed his ways, but the fox may grow grey, but never good.
Don't trust his sudden kindness; remember that the fox may grow grey, but never good.