Optical materials with colour changing abilities have been explored for use in display devices1, smart windows2,3 or in the modulation of visual appearance4–6. The efficiency of these materials, however, has strong wavelength dependence, which limits their functionality to a specific spectral range. Here, we report graphene-based electro-optical devices with unprecedented optical tunability covering the entire electromagnetic spectrum from the visible to microwave. We achieve this non-volatile and reversible tunability by electro-intercalation of lithium into graphene layers in an optically accessible device structure. The unique colour changing capability, together with area-selective intercalation, inspires the fabrication of new multispectral devices, including display devices and electro-optical camouflage coating. We anticipate that these results provide realistic approaches for programmable smart optical surfaces with a potential utility in many scientific and engineering fields such as active plasmonics and adaptive thermal management.By converting Li-ion battery into an optical device using graphene electrodes, an electrochemical optical device which enables colour changing ability over the entire wavelength range from visible to microwave is demonstrated.