Metal nanovoids are grown on a stretchable plastic film. The fabrication proceeds by assembling the template of a single layer of close packed silica spheres on a conducting substrate. A conducting layer is then electrochemically grown on top to form a master. An elastomeric precursor is then coated on the master (e.g. by spinning) and is cured before removal. The resulting plastic film is then coated with a thin (e.g. 20 nm) layer of noble metal (e.g. Au, Ag or Cu), to produce a flexible film. Applications for such tuneable structural colour would be coating of injection moulded artefacts, such as mobile phone covers, car bodies to form an iridescent skin, wall and fascia decorations, loudspeaker coatings, architectural tent coverings, and clothing.