o 626 nm basic blue 3 654 nm methylene green 657 618 nm taylor 39 s blue 649 nm janus green b 660 395 nm meldola 39 s blue 570 nm new methylene blue 630 591 nm thionin 598 nm nile blue 638 nm celestine blue 642 nm a method of synthesis of leucomethylene blue and the oxygen dependent reoxidation to form the colored form of the methylene blue dye is shown below in addition to the above reactive materials numerous other dyes and light blocking materials can be synthesized to operate to render the data storage media limited play for example some other possible reactive materials can be found in u s pat no 4 404 257 hereafter incorporated by reference and u s pat no 5 815 484 hereafter incorporated by reference the reactive materials can further comprise a mixture comprising at least one of any of the above mentioned reactive materials the reactive material is preferably mixed with a carrier for deposition on and or impregnation into at least a portion of the surface of the substrate possible carriers comprise the thermoplastic acrylic polymers polyester resins epoxy resins polythiolenes uv curable organic resins polyurethanes thermosettable acrylic polymers alkyds vinyl resins and the like as well as combinations comprising at least one of the foregoing carriers polyesters include for example the reaction products of aliphatic dicarboxylic acids including e g fumaric or maleic acid with glycols such as ethyleneglycol propyleneglycol neopentylglycol and.