The recent emergence of bound states in the continuum (BICs) has established a powerful paradigm for achieving high-quality-factor resonances in metasurfaces. Here, we propose a silicon nitride metasurface structure capable of supporting polarization-sensitive quasi-BICs, to generate structural colors with a wide gamut, high saturation, and tunable brightness. By designing a periodic array of nanodisks with in-plane symmetry breaking, we successfully excite magnetic dipole quasi-BICs with polarization-sensitive properties. Owing to its high-quality factor, this resonance exhibits a narrow-linewidth reflection peak across the visible spectrum, thereby significantly enhancing color purity. We employ a synergistic approach that combines deep learning with reinforcement learning to efficiently predict the optimal structural parameters, resulting in coverage that approaches the simulated sRGB color gamut. Experimental results further demonstrate that the brightness of the structural colors can be dynamically tuned by controlling the polarization state of incident light. Based on this mechanism, we design and fabricate two categories of chromatic patterns with orthogonally arranged air holes, which exhibit clear polarization-dependent responses under both orthogonal linear polarizations and white-light illumination. Our work offers insights into the application of high-performance structural colors in color printing, dynamic information encryption, and optical anticounterfeiting.

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• Bound states in the continuum
• Fano resonance
• Nanophotonics
• Polarization of light
• Metasurfaces
• Deep learning
• Finite-element method
• Reinforcement learning