He acted as a 'foil for' the comedian. [=he acted very serious to make the comedian seem funnier]
His reserved manner was a perfect 'foil for/to' her bubbly personality.
That dark blue dress is good 'foil for' her blonde hair.
(..) DOC: Get in! Yes! MARTY: There he is, Doc! - Let's land on him and cripple his car. - That's a ' Ford. We're a DeLorean. DOC: He'll rip us like tin foil. - So what do we do? - I have a plan. RADIO: RADIO: - Shit. (..)1989 Back to the Future Part II