Researchers have figured out how to use a specific engraving technique in order to alter the frequency of light a metal—any metal—absorbs or reflects. How? By carving tiny rings, smaller than the wavelengths of light.
Gold normally absorbs blue light, which gives it its yellowish hue. Silver metals absorb and emit just about every frequency of visible of light (which means… they’re actually colorless).
This is essentially the same technique that scientists are using to create invisibility cloaks, except that instead of trying to make light pass through a material, they just want to redirect how light is reflected and absorbed. [Technology Review]