There are four directions on the outer wall, representing different five elements. Any color will produce certain symbiosis or mutual resistance, which is not conducive to Feng Shui. Therefore, we can't judge the square tile comprehensively by the color of geomantic omen, but only from the aesthetic point of view.
As far as the geomantic omen of the gate is concerned, the Western Wall belongs to gold, and you can choose yellow (belonging to soil, borrowing soil to make gold auspicious) or white (belonging to gold, auspicious), and avoid red and green.