A light source is configured to emit a narrow peak at a discrete spectral band, especially at a primary color wavelength. The light source can have a plurality of narrow peaks to simulate the effect of a broadband light source. A subject is provided with a pigment, such as certain rare earth lanthanides, with a strong absorption peak at a corresponding narrow spectral band. The pigment has a nominal color when illuminated by a true broadband light (e.g., sunlight) that does not have a narrow peak at the discrete spectral band, and has a different color when illuminated by the light source that has a narrow peak. This color shift can be used for security authentication, information and decorative applications.