Illumination sources and subjects having distinctly matched and mismatched narrow spectral bands

In combination, a light source and a subject, wherein, the light source has an illumination spectrum characterized by a plurality of narrow peaks within a spectrum;

• the subject has a pigment applied thereto, wherein the pigment has a reflection spectrum characterized by one or more reflection gaps;
• the pigment gives the subject a distinct appearance when illuminated by the light source due to a color shift from at least one of the narrow peaks matching one or more of the reflection gaps, as compared to a nominal appearance when illuminated by a broadband light source.

A method for producing a detectable change in appearance, comprising the steps of:

• applying a pigment to a subject, the pigment having at least one reflection gap within a reflective spectrum;
• illuminating the subject with a first broadband light source having an illumination spectrum encompassing the reflective spectrum of the pigment, whereupon the subject has an appearance that is nominal;
• subsequently illuminating the subject with a second light source characterized by a visible illumination spectrum with discrete illumination bands, wherein at least one of the illumination bands overlaps the reflection gap of the pigment, thereby visibly changing the appearance of the subject to be different than nominal.