all cats are grey by night

Proverb

all cats are grey in the dark

1. (UK, offensive, sometimes, vulgar) Sex is enjoyable regardless of the physical attractiveness or social station of one's partner.
   • [Of a widow:] And to make carnall appetite content,
     To take lacke of beautie but as an eye ſore.
     The fayre and the foule, by darke are lyke ſtore.
     When all candels be out, all cats be grey,
     All thingis are then of one colour, as who ſey.
     And this prouerbe ſaith, for quenching hot deſyre,
     Foule...1562, John Heywood, A Dialogue Conteynyng the Number of the Effectuall Proverbes in the Englishe Tounge..., page 10
2. (uncommon) Under some circumstances, individual distinctions are not relevant.
   • In such a darkness, in which all cats are grey, Lucrezia Borgia might well seem as white as a blue-eyed Persian. But the paradox remains that Corvo might not impossibly be right. As, but for superhuman strainings, Dreyfus might have gone down to history as a traitor to France, so may the Borgian...1907, Israel Zangwill, Italian Fantasies, page 167