Subwavelength metallic gratings were proposed as integrated polarized-RGB (red, green, and blue) color filters here and their performance was further numerically optimized with the rigorous coupled-wave analysis (RCWA) method and the genetic algorithm (GA). Grating types include the single-layer type and the double-layer one while parameters to be optimized are the period, filling factor, and thickness of each layer. The ideal performance is defined both by the large extinction ratio over the visible range and by the high transmittance aiming at wavelengths of 700 nm (R), 546.1 nm (G), and 435.8 nm (B). Results showed that a double-layer grating achieves about 50% transmission efficiency and a large extinction ratio (60dB), which are better than those in previous studies. If the proposed design can integrate with popular liquid crystal display panels, a promising way can be paved to reduce the volume and cost of display electronics.