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We report a new metallic silvery color caused by nano-to micro-pointillistic mixing of disordered pixels of iridescent colors, which result from a multilayer reflector.

Here, we report a two-dimensional (2D) amorphous photonic structure (APS) discovered in the central layer of the periostracum of the mussel Perna canaliculus, based on field emission scanning electron microscopy, X-ray diffractometer, attenuated total reflection Fourier transform infrared spectroscopy, and fiber optic spectrometry combined with the image processing technology and pair correlation function analysis. This APS contains ~29% in volume of protein fibers embedded in a protein matrix. These fibers, with diameters of 103 ± 17 nm, are densely arranged and unevenly crimped. In addition, they are locally parallel with each other and exhibit short-range order with a nearest-neighbor distance of 189 nm. Interestingly, the APS is humidity-responsive with a vivid green structural color (~530 nm) in the wet state, which disappears in the dry state. Moreover, the APS is sandwiched by two dense layers in the periostracum, which is flexible in wet and can spontaneously or artificially deform into various shapes. We hope this APS may provide new inspirations for the design and synthesis of 2D amorphous photonic materials.

We proposed a schematic model of the fiber architecture in the fibrous ligament (FL) of A. marissinica.