Green’s Dictionary of Slang

1. frequented by homosexuals.

1963

G. Lambert Inside Daisy Clover (1966) 18: Next to it there’s a minty cafe which serves homemade chilli.

2. effeminate in mannerism, if not actually homosexual.

1965		Guild Dict. Homosexual Terms 30: mintie (adj.): Effeminate.
1972		B. Rodgers Queens’ Vernacular.
1977		A. Ebert Homosexuals 174: In other words, the ‘Gay Hairdresser,’ the minty queen with a hair dryer who blow cuts, blow dries and blow jobs, is a myth.
1980		Maledicta IV:2 (Winter) 238: A great many minty men and butch women are completely heterosexual.