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Colour is of special interest in chemistry, physics, biology, medicine and of course for culture and life style. The relation between colour and constitution of organic materials at molecular level, to be called mono molecular colour phenomenon (MMCP), is well understood based on PPP-MO calculations of energy levels of excited states upon light absorption. However, such a relation cannot always be extrapolated to supramolecular state in which colorants normally exist both in nature and for their actual functionality. The present study provides examples of both mono molecular colour phenomenon (MMCP) and supramolecular colour phenomenon (SMCP), and a rationale of their differentiation.