Reveal her true colours - Idioms by The Free Dictionary
reveal (one's) (true) colors (redirected from reveal her true colours)
reveal (one's) (true) colors
To reveal what one really believes, thinks, or wants; to act in accordance with one's real personality, character, or disposition. Primarily heard in US. Dave said all along that he only wanted this deal because it was in the company's best interest, but he revealed his true colors once he realized that he wouldn't get any special commission for his efforts. It's only in times of crisis that your friends will really reveal their colors.
References in periodicals archive
In her speech outside Number 10 on becoming PM, Mrs May claimed she wanted to look after the less well off in our country, but it hasn't taken her long to reveal her true colours
She prodded the right people at the right time and allowed Eileen Drewery to reveal her true colours
when she suggested to a girl who'd lost one eye that she probably deserved it after "being a bit evil" in a previous existence.