Qualitative results of an x‐ray photoelectron and optical investigation of three thin‐film transition‐metal oxides, namely, WO3, MoO3, and V2O5are reported. Data were obtained on films that werenotcoloredandcoloredby an electrochromic process. The particular electrochromic coloration process used is electrolytic in nature and employs a sandwich‐structure electrochromic cell and electrolyte pool. The optical spectra show increased absorption in the visible (red) and near‐infrared spectral regions upon coloration. The photoelectron spectra forcoloredfilms exhibit a small band near the Fermi level and asymmetric band shapes for metal core‐level bands which are absent in films that arenotcolored. The new band and the asymmetric band shapes are attributed to the presence of a reduced‐state species caused by the presence of trapped electrons and metal bronze formation. Results from coloration with different electrolyte pools, i.e., H+, Li+, Na+, K+, Cs+, and Mg2+electrolytes, are reported.