AbstractReflective structural colors have backlight‐free supremacy and can provide energy‐efficient and environmental‐friendly color production for many applications. However, they are hindered by the complex process and incorrect colors after fabrication. Here, a pixelated electrothermal oxidation technique is proposed that can precisely tailor and produce reflective structural colors covering the entire visible range, providing the possibility for customized structural color filter arrays from a titanium canvas. Furthermore, as a demonstration, a photonic‐firework‐like color filter array is achieved in a single step via thermal engineering. Based on this one‐step‐forming color array, a computational spectrometer is also realized featuring a resolvability of 10 nm and operating bandwidth covering the whole visible range. Considering its compactness and mass production capability, this method has numerous potential applications in, e.g., imaging, anti‐counterfeiting, printing, color display, and spectroscopy.