show colors

show (one's) (true) colors

To reveal what one really 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

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
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.
The entire site has been redesigned and now features the new logo, show colors and exciting changes that exhibitors and attendees alike will enjoy.
Besides poppies, there are also early blooms from blue pygmy lupines and tiny yellow flowers called goldfields along western Antelope Valley roads, which are usually the first places to show colors.
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.
We show colors, but the whites and naturals do the best -- they're basics.
they cannot show colors or support video graphics, monochrome monitors
For example, a graphic designer could set her display to show colors exactly as they appear on a printed page.