Plasmonic effects in Au–Ag nanostructures are utilized to realize novel electrochromic device. A quasi ordered Au–Ag core–shell nanoparticle array is realized by thermal evaporation of Au and electrochemical deposition of Ag into a SiO 2 hole array assisted by anodic aluminium oxide membranes. The thickness of the Ag shell could be changed by alternating the electrochemical deposition time: as a result, the color of the device can be widely and quasi‐reversibly tuned through this electrical control.