A novel thiophene derivative (Fe-Th) with ferricyanide end group is successfully synthesized. The polythiophene derivative (Fe-PTh) is additionally obtained in aqueous solution by polymerization of Fe-Th, and shows a nanoparticle structure with a diameter from 10 to 100 nm. A simple solid-state electrochromic device is fabricated using the Fe-PTh as electrochromic material, and displays a novel three-color electrochromism from blue, green, and red with the increased potential.