• НОЧЬЮ <B ТЕМНОТЕ> ВСЕ КОШКИ СЕРЫ
[saying]
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⇒ differences between people, things etc of a certain kind are indistinguishable in the dark, or under circumstances that obscure those differences:
- all cats are gray in the dark.
Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. С.И. Лубенская. 2004.