A system for recording and/or transmitting optical data or visual images includes an optical data or visual image recording medium and a light and/or heat source. The medium includes a markable coating established on a substrate. The markable coating includes a leuco dye and a developer precursor including a compound that undergoes rearrangement in response to a stimulus, thereby forming a developer that reacts with the leuco dye. The light/heat source is positioned so as to illuminate and/or heat the medium in a predetermined manner to i) cause photochemical and/or photothermal rearrangement of the developer precursor to form the developer which reacts with the leuco dye to form an optically detectable mark, or ii) cause at least one optically detectable mark previously formed on the markable coating to produce at least one readable pattern.