Tungsten trioxide (WO3) thin films have been prepared on the flexible indium tin oxide (ITO) substrates by pulsed laser deposition (PLD) using WO3 targets in oxygen gas. Color of the WO3 film on the flexible ITO substrates depends on the oxygen gas mixture. The plasma plume produced by PLD using a Nd:YAG laser and WO3 target is investigated by temporal and spatial-resolved optical emission spectroscopy. WO3 films prepared on the flexible ITO substrates show electrochromic properties, even when the substrates are bent. The film color changes from blue to transparent within 10-20 s after the applied DC voltage is turned off. Published by Elsevier B.V.