Herein, we demonstrate electrochromism of charged inverse opal photonic gel (IOPG) in aqueous solution for full color reflective display. Opal-templated polymerization of hydroxyethyl methacrylate with ionizable monomer and subsequent etching formed the IOPG exhibiting a structural color by Bragg diffraction of light. The IOPG contained acrylic acid (AA) (or vinyl imidazole (VI)) that can be ionized above the pKa (or below the pKb) of the gel. Application of 4 V bias induced apparent color changes of the AA-IOPG from red to green due to decreased osmotic pressure within the IOPG near the ITO surface. It was revealed that the local pH change by water-splitting under voltage bias is the main driving force for IOPG deswelling. The blue shift of the colors during voltage ON was found to be faster than the red shift at voltage OFF due to the electrophoretic migration of protons. The VI-IOPG, which swells at low pH due to a positively charged hydrogel, showed a slight red shift of the reflective color by voltage ON and blue shift upon when voltage OFF. The reproducible color changes of AA-IOPG upon the repeated ON/OFF bias clearly showed that the IOPG can be a promising candidate for a reflective display.