a Schematic of the sample with Ag nanoclusters on a spacer with gradually varying thickness along the diagonal. b Photographic image of the structure depicted in a, with rainbow-like colours starting from black along the diagonal where coupling strength is tuned. c The diverse colour generation in CIE 1931 xy chromaticity diagram with black dots calculated from the spectra from Fig. 3c and the sRGB gamut outlined in white lines. d Digital copy of the painting (Peony Flower). e The fabricated hybrid structure. The scale bar represents 10 mm.