Certain mechanical structures create colors when they are illuminated by light. This is achieved whenever a wide illuminating spectrum is filtered through some physical processes such as diffusion, scattering, or interference. Periodicity in the structures generally leads to iridescence as in the case of opals and holograms; conversely, interferential construction can generate broad band spectra such as the ones displayed at the reconstruction stage of some Lippmann color photographs. The characteristics of the materials and processes used to make such pictures are enhanced through an analysis of their microstructure. Energy spectra generated by interference in resonant structures and in Lippmann photographs relate closely to the volume distribution of the scatterers they are made of.