Adjective
(as) white as a sheet
(simile, said of a human's complexion) Very white or pale, as if suffering from shock.
Synonym: pale as a ghost
Hitler would go as white as a sheet and tightly clench his jaws, while his eyes would dilate. Everyone in his entourage would get panicky because these fits were always followed by an order to dismiss or to execute somebody. Theodor Morell