The blue colour is described as "dark sky-blue", and varies from flag to flag, ranging from a hue of pure blue, sometimes shaded almost as dark as navy blue, to hues about 75% toward pure cyan and shades as light as very light blue. The flag was designed for the Zionist Movement in 1891. The basic design recalls the ' (), the Jewish prayer shawl, which is white with black or blue stripes. The symbol in the center represents the Star of David (', ), a Jewish symbol dating from late medieval Prague, which was adopted by the First Zionist Congress in 1897.