A moire magnification device is disclosed, comprising a transparent substrate carrying: a regular array of micro-focusing elements on a first surface, the focusing elements defining a focal plane; a corresponding first array of microimage elements in a first colour and located in a plane substantially coincident with the focal plane of the focusing elements; and a corresponding second array of microimage elements, in a second colour different from the first colour, and located in a plane substantially coincident with the focal plane of the focusing elements, the second array of microimage elements being laterally offset from the first. The pitches of the micro-focusing elements and first and second arrays of microimage elements and their relative locations are such that the array of micro-focusing elements cooperates with each of the first and second arrays of microimage elements to generate respective magnified versions of the microimage elements of each array due to the moire effect. An interruption zone of non-zero width is perceived between the between the magnified version of the first microimage array and the magnified version of the second microimage array, the interruption zone exhibiting no magnified version of either microimage array. Also disclosed are a method of manufacturing a moire magnification device, and a security document.