The invention relates to a multi-layered foil body (1) for marking a security document, in particular a banknote. The foil body (1) has at least one colour filter layer (2) and at least one change layer (4) with an electrically controllable transmittance and/or an electrically controllable colour. The change layer (4) can have liquid crystals (15), which are alignable in an electric field, such as a PDLC layer. The foil body (1) preferably comprises two differently coloured colour filter layers (2, 3) and a change layer (4) which is disposed therebetween. The invention furthermore relates to a security element (10) having at least one aforementioned foil body and a piezoelectric energy source (8) which controls the change layer (4).