show colors

show (one's) (true) colors

To reveal what one truly believes, thinks, or wants; to act in accordance with one's real personality, temperament, or disposition. Dave said all along that he only wanted this deal because it was in the company's best interest, but he showed 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 show their colors.
See also: color, show
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.

show one's (true) colors

Fig. to show what one is really like or what one is really thinking. Whose side are you on, John? Come on. Show your colors. It's hard to tell what Mary is thinking. She never shows her true colors.
See also: color, show
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
See also:
References in classic literature ?
Then the green things began to show buds and the buds began to unfurl and show color, every shade of blue, every shade of purple, every tint and hue of crimson.
This includes the new Enhanced Ambient Mode, which will be able to show colors (up to 16 colors) on the screen, support adaptive brightness and show live complications.
The entire site has been redesigned and now features the new logo, show colors and exciting changes that exhibitors and attendees alike will enjoy.
A centrist member of the PRI, the former Tlaxcala governor has yet to show colors in the current Congress, where she leads the single largest bloc of deputies of any party.
9, designed to show colors available to advertisers.
We show colors, but the whites and naturals do the best -- they're basics.