3,4-Ethylenedioxy thiophene is polymerized electrochemically in p-toluene sulphonic acid (a), phosphate buffer (b) and borax buffer (c) on glassy carbon and Indium tin oxide (ITO) surface. The scan rate dependence studies of the polymer redox processes were carried out. A linear relationship was observed between the peak current and scan rate with good correlation, r(2) = 0.998 indicating adsorption controlled behaviour of polymer film. The SEM photograph showed the differences in surface morphology of polymers modified electrode. The XRD studies revealed semi-crystalline nature of doped polymers. Spectroelectrochemical behaviors of Indium tin oxide coated glass electrode covered with thin film of poly-3,4-ethylenedioxythiophene a, b, c in 0.1 M KCl were obtained at different electrode potentials between 1100 and 200 nm. Poly-3,4-ethylenedioxythiophene-a, poly-3,4-ethylenedioxythiophene-b and poly-3,4-ethylenedioxythiophene-c film exhibits transparent clear blue, opaque violet and dark maroon colours respectively at reduced potential. Further probing the potential between 400 mV and 800 mV coated film shows greenish blue colour for poly-3,4-ethylenedioxythiophene-a, poly-3,4-ethylenedioxythiophene-b and poly-3,4-ethylenedioxythiophene -c shows opaque violet and yellowish maroon colours respectively. Increasing the applied potential between 1000 mV and 1200 mV over oxidation of polymer film shows dark greenish blue for poly-3,4-ethylenedioxythiophene -a, dark brown for poly-3,4-ethylenedioxythiophene-b and transparent red colour for poly-3,4-ethylenedioxythiophene-c. Electrochromic parameters such as colouration efficiency, response time and optical contrast were calculated for all three films. (C) 2013 Elsevier Ltd. All rights reserved.