  Stochastic inhomogeneous oxidation is an inherent characteristic of copper
(Cu), often hindering color tuning and bandgap engineering of oxides. Coherent
control of the interface between metal and metal oxide remains unresolved. We
demonstrate coherent propagation of an oxidation front in single-crystal Cu
thin film to achieve a full-color spectrum for Cu by precisely controlling its
oxide-layer thickness. Grain boundary-free and atomically flat films prepared
by atomic-sputtering epitaxy allow tailoring of the oxide layer with an abrupt
interface via heat treatment with a suppressed temperature gradient. Color
tuning of nearly full-color RGB indices is realized by precise control of
oxide-layer thickness; our samples covered ~50.4% of the sRGB color space. The
color of copper/copper oxide is realized by the reconstruction of the
quantitative yield color from oxide pigment (complex dielectric functions of
Cu2O) and light-layer interference (reflectance spectra obtained from the
Fresnel equations) to produce structural color. We further demonstrate
laser-oxide lithography with micron-scale linewidth and depth through local
phase transformation to oxides embedded in the metal, providing spacing
necessary for semiconducting transport and optoelectronics functionality.
