Indigo is a unique organic compound in terms of its blue color and its multiple conjugated functional groups contained therein. We ask whether the enthalpy of its cleavage reaction into two isatin molecules reflects the novelty of either this color and/or the conjugated functionalities contained therein.Indigo, species 1, is quite unique among organic compounds. It has a unique "eponymic" blue color and extensive historic provenance and importance in numerous cultures in both the Western and Eastern hemispheres (cf. the derivation of the word "indigo" from "India"). Both of these aspects, the color and the importance, have shown fading-there are now other dyes of diverse and popular hues that fill the rainbow-rich human-derived landscape of fabrics and other materials. The blue color slowly fades in objects of art and commerce colored by indigo as the central C=C bond is cleaved by air and other ubiquitous oxidants.