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

1.
menunjukkan sifat sebenar seseorang, mendedahkan diri sebenar seseorang
to reveal someone's true character, especially if it is negative or unpleasant
:
•
The crisis really showed him in his true colors.
Krisis itu benar-benar menunjukkan sifat sebenarnya.
•
His actions eventually showed him in his true colors to everyone.
Tindakannya akhirnya menunjukkan sifat sebenarnya kepada semua orang.