show someone in their true colors

US /ʃoʊ ˈsʌm.wʌn ɪn ðer truː ˈkʌl.ərz/
UK /ʃoʊ ˈsʌm.wʌn ɪn ðer truː ˈkʌl.ərz/
"show someone in their true colors" picture
1.

iemand in zijn ware aard laten zien, iemands ware gezicht tonen

to reveal someone's true character, especially if it is negative or unpleasant

:
The crisis really showed him in his true colors.
De crisis liet hem echt in zijn ware aard zien.
His actions eventually showed him in his true colors to everyone.
Zijn acties toonden hem uiteindelijk in zijn ware aard aan iedereen.