  Structural colours have drawn wide attention for their potential as a future
printing technology for various applications, ranging from biomimetic tissues
to adaptive camouflage materials. However, an efficient approach to realise
robust colours with a scalable fabrication technique is still lacking,
hampering the realisation of practical applications with this platform. Here we
develop a new approach based on large scale network metamaterials, which
combine dealloyed subwavelength structures at the nanoscale with loss-less,
ultra-thin dielectrics coatings. By using theory and experiments, we show how
sub-wavelength dielectric coatings control a mechanism of resonant light
coupling with epsilon-near-zero (ENZ) regions generated in the metallic
network, manifesting the formation of highly saturated structural colours that
cover a wide portion of the spectrum. Ellipsometry measurements report the
efficient observation of these colours even at angles of $70$ degrees. The
network-like architecture of these nanomaterials allows for high mechanical
resistance, which is quantified in a series of nano-scratch tests. With such
remarkable properties, these metastructures represent a robust design
technology for real-world, large scale commercial applications.
