Two designs of high color purity RGB color filter (RGB-CF) using Fabry-Perot etalon were proposed. First, various transmission spectra for corresponding pixel arrays were achieved by optimizing the orientation of fixed polymerized liquid crystal polymers with high birefringence. The designed high color purity RGB-CF is believed to have potential for display applications. Second, three primary transmissive peaks for each pixel were achieved with the optimized air gap. Compensated CFs were adopted to enhance color purity by absorbing undesirable transmissive light. The second design is to overcome the limitation of the cell gap in the first design. Additionally, two approaches to improve light utilization efficiency were discussed.