The Flag of the Soviet Union
The Soviet Union flag used a bright shade of red; this was typical for flags of communist countries. On the flag, a hammer and sickle could be found. This originated from unity of Russian workers (hammer) and Russian peasants (sickle) that together were to form the Soviet state. The red color represented the blood that was spilt by workers, who fought for their emancipation. On the flag, you could also find a single yellow star, which was supposed to represent life and the energy of the sun. The five connected points of the star symbolized unity and diverse representation of the government.
Work cited: http://www.crwflags.com/fotw/flags/su.html