At Twilight Come the Flesheaters.

Digiorno (Timo) and his pals gather one evening to watch a black and white zombie porn flick. In this dual storyline (in color and monochrome) it's difficult to tell who the real monsters are: the backstabbing "friends" in the color sequences or the flesh-hungry, sex-crazed zombies in the black-and-white sequences. Friends reveal their monstrous sides. Elusian is the chrome-dome club-kid, and DiGiorno, Elusian's ex-lover, is emotionally stunted and can only communicate and perceive life through sex. A tale of coitus, cat-fighting and conspiracy.