There are different types of devices, based on substrates (glass vs plastic) and where the electrochromic material is located (in solution or on the substrate). Glass/in solutions architectures are typically used for smart glass and smart windows. plastic/on substrate solutions are typically used for displays. NTERA (www.ntera.com) sells a simple kit to printers who can try it out. It required screen printing press and dryer.

I believe it is called Electrochromic

An electrochromic rearview mirror is installed on higher end vehicles. It consists of two lenses that sandwich an electrochromic (electronic color changing) gel. This gel, when charged with electricity, darkens. The mirror uses a forward sensor which measures the outside ambient light, and a rearward sensor to look for glare. When dark enough, it sends current to the electrostatic gel, darkening it a rate which is related to the level of ambient darkness and rearward glare. When the outside ambient light increases, the current decreases, until the gel is clear again at daylight light levels. The inside sides of the lenses are coated with a transparent, conductive layer, and the deepest lens has a reflective (mirror) coating. There is no tab to pivot the mirror. For more info, see: www.gentex.com/auto_how_nvs_work.html.

Nickel oxide films are classified as electrochromic materials for which the optical absorbance (A) change under insertion (by electrochemical methods) of small cations like H+ (protons) and Li+. The coloration efficiency (CE) is defined for electrochromic materials as the change in the optical absorbance per unit of inserted charge Q, i.e, CE=(A1-A2)/Q, where Q is the inserted charge that promoted the (A1-A2) change in the optical absorbance of the nickel oxide film.

Rhodium Chains do change colors. The rhodium has a mirror like reflecting appearance. The rhodium chains are a two color electrochromic system. This gives the rhodium chains a look of having multiple colors.