Abstract: A light emitting polymer diode device for obtaining voltage controlled colors, based on thin polymer films incorporating more than one electroluminescent conjugated polymer and zero or more non-conjugated polymers, and where this polymer blend is formed by mixing the different polymers in a common solvent, which electrolumincscent polymers phase separate in the polymer blend with domains of polymers that have a diameter comparable with the thickness of the polymer film, where the polymer film is sandwiched between two electrodes, one of which injects electrons and one which injects holes, possibly with electron and hole transport layers in between the polymer layer and the electrodes, and where the electrons and holes form excitons in the polymer film leading to emission of photons with colors determined by the bandgap of the emitting materials, and in which the more than one conjugated polymers have different emission colors, and where the polymers of lower bandgap emit light at a lower applied voltage than