A lustre layer is a decorative layer applied to a white opaque glaze in pottery famous for its metallic sheen. Lustreware is effectively a multi-layered structure. The paper discusses the importance of the spatial distribution of silver (Ag) and copper (Cu) nanoparticles in lustre glazes in determining the decorative colour. Using Scanning Transmission Electron Microscopy and energy dispersive x-ray analysis (STEM-EDX) of cross sections, this distribution is easily imaged, as the authors demonstrate on two modem reconstructions of lustre decorations from Granada, Spain. On the nanoscale, the difference in colour can be related to a different spatial distribution of the Ag and Cu particles, with the brownish gold variant consisting of a top layer of Ag nanoparticles and an underlying layer of Cu nanoparticles, while in the yellowish golden lustre Cu specks are unevenly dispersed. -- ICCROM