PEDOT [poly (3,4-ethyldioxythiophene)] films have been electrochemically prepared in mixed solution of boron trifluoride diethyl etherate and tetrahydrofuran (BFEE-THF). The film shows tricolor electrochromism which is claret red at -0.8 V, light grey at 0.2 V, and sea blue at 1.0 V. The film retains 74% of the original electroactivity and unperturbed electrochromic behaviors after 3000 cycles indicating potential applications on EC devices. Spectroelectrochemistry indicates that the -* transition absorption peak (max) in the neutral state is located at 512 nm and the calculated energy gap (Eg) is 1.76 eV by the onset wavelength. Compared to the electropolymerization of PEDOT films in conventional solvent, tricolor electrochromism can be ascribed both to the low onset oxidation potential and polymerization rate in BFEE-THF, which may result in a low conjugation length of PEDOT. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013