poner algo negro sobre blanco: expresar algo con claridad, normalmente en forma escrita.
-Ha llegado el momento de poner negro sobre blanco las posturas actuales — The time has come to set down, in black and white, our current positions
-Este escándalo ha puesto negro sobre blanco una realidad mil veces denunciada — By seeing it down in writing, in black and white, this scandal has laid bare a reality that has been denounced a thousand times
-El PP exige que se ponga negro sobre blanco la nueva reforma — The PP have called for them to put the new reform down in black and white
