In this study, a new electroactive monomer, 3-(244-(2,5-di-2-thienyl-1H-pyrrol-1-yl)phenyl]ethyl-thio)propanoic acid (SNSPA), was synthesized and then deposited onto the ITO/glass surface by an electrochemical process. When positive potentials were applied on the polymer film of SNSPA, the film at the neutral state turned from orange to green (0.6 V) and then to blue (1.1 V) because of the presence of polaronic and bipolaronic species on the SNS main chain of the polymer. At the last stage, a complementary electrochromic device was constructed by using poly(SNSPA) as the anode layer and PEDOT:PSS as the cathode layer. A fast response time (about 0.5 s) and a high stability of about 98% were obtained at the end of 1000 cycles. The capability of the proposed polymer to undergo reversible color change among brown, green, and blue is a significant property for use as an adaptive camouflage material for all conditions of sand, forest, and sea for military applications.