The present invention relates to a planar sealing element (1) for application to a substrate (2), comprising a carrier layer (3) and several functional layers (4),



the functional layers (4) comprising at least one colour display layer (5) and an adhesion-controlling layer (6),
the sealing element (1) furthermore comprising an adhesive layer (8) for attachment to the substrate (2),
the functional layers (4) being arranged between the carrier layer (3) and the adhesive layer (8),
wherein the carrier layer (3) is at least partially detachable from the functional layers (4) in order to bring the sealing element (1) from a first state (9) to a second state (10), with the second state (10) not being convertible into the first state (9),
the sealing element (1) in the second state (10) comprising a peeled-off layer (11), comprising at least the at least partially detached carrier layer (3), and a residue (12), comprising at least the adhesive layer (8) and at least parts of the at least one colour display layer (5),
the carrier layer (3) being made of paper, wherein it is envisaged, according to the invention, that the carrier layer (3) is translucent so that the peeled-off layer (11), in at least one area when the peeled-off layer (11) is arranged congruently on the residue (12), has a different colour impression than the same area of the carrier layer (3) in the first state (9) in a viewing direction toward the carrier layer (3).