The mechanisms for electrochromism of various phases and morphologies of tungsten oxide have been heavily debated in the last several decades, but these results demonstrate that multiple different mechanisms may be operative depending on the interaction between intercalating cations and the electronic states and crystal lattice. The presence of a different spectral line shapes for films reduced in Li + and Na + electrolytes suggests that, in addition to the increase in free electrons, some portion of the injected electrons localize.