Diffusion aside, all colors generated by photonic structures are very sensitive to the direction of incidence of light. We have seen that at the nanometric scale, a topological disorder or a local deformation can reduce or even eliminate this iridescence: the presence of photonic poly-crystals leads to a mixture of colors which desaturates them and disperses the reflection. But similar effects can also occur on a microscopic or macroscopic scale with the deformations of the different supports of the structures (Fig. 14.1).