The flag of Poland consists of two horizontal stripes of equal width, the upper one white and the lower one red. The two colors are defined in the Polish constitution as the national colors. A variant of the flag with the national coat of arms in the middle of the white stripe is legally reserved for official use abroad and at sea.
White and red were officially adopted as national colors in 1831. The flag is flown continuously on the buildings of the highest national authorities, such as the parliament and the presidential palace. Other institutions and many Polish people fly the national flag on national holidays and other special occasions of national significance. (source)