The present invention provides improved spectral signature strategies for use in a wide range of product and service applications. The present invention encodes spectral signature features into one or more optical brightener compounds and/or one or more infrared absorbing compounds. Equipment is modified with appropriate ultraviolet/violet or infrared LED illumination sources and corresponding detectors, optionally optical filters, and optionally mask elements, in order to read the spectral responses. These features desirably are used in combination with one or more other luminescent taggant compounds.