Green’s Dictionary of Slang

who in hell...? phr.

also who in red hell...?

a general intensifier for a question.

[US]Tomahawk (White Earth, Becker Co., MN) 19 Oct. 3/5: Who in all-fired hell are you talkin’ about?
J. Masefield Victorious Troy 68: ‘Who in hell said “Time, too?”’ Cobb asked [...] ‘Which of your damned packet-rats said “Time, too”?’ .
[US]C. Himes Crazy Kill 29: Who in the God-damned hell’s going to bring him in?
[US]B. Hecht Gaily, Gaily 96: Who in hell knows her name?
[US]R.M. Brown Southern Discomfort (1983) 78: A pounding at the back door scared her. ‘Goddamit!’ [...] ‘Who in fucking red hell is it?’.