Green’s Dictionary of Slang

a pornographic film.

1998		K. Sampson Awaydays 94: Watching one of the higher art forms, a double-bill of German blueys called Grunt and The Fishmonger.
2004		P. Howard PS, I Scored the Bridesmaids 110: I go downstairs to pay the bill [...] not wanting Sorcha to find out about all the blueys I watched.