  Structural coloring is a photostable and environmentally friendly coloring
approach that harnesses optical interference and nanophotonic resonances to
obtain colors with a range of applications including steganography, d\'ecor,
data storage, and anticounterfeiting measures. We show that optical coatings
exhibiting the photonic Fano Resonance is an ideal platform for structural
coloring -- it provides full color access, high color purity, high brightness,
controlled iridescence, and scalable manufacturability. We show that an
additional oxide film deposited on Fano resonant optical coatings (FROCs)
increases the color purity (up to 97%) and color gamut coverage range (> 99%
coverage of the sRGB and Adobe color spaces). For coloring applications that do
not require high spatial resolution, FROCs provide a significant advantage over
existing structural coloring schemes.
