When it comes to metal, you can have any colour as long as its silver. That’s because the sea of electrons within most metals absorbs and emits light over the entire optical range. Rather than silver, metals are actually colourless. There are exceptions, of course. Gold absorbs blue light and this produces its characteristic yellow colour. And copper absorbs blue and green light making it look a reddy orange. Other colours are hard to come by without coating the metal or carving a diffraction grating onto its surface to produce a characteristic interference pattern, like those from a compact disc. But now there’s another way thanks to some interesting work by Jianfa Zhang at the University of Southampton and a few pals. Their idea is to carve a different type of repeating pattern on to the surface of a metal.