The Olympic rings cover every flag in the world. Yellow, green, red, black, and blue were selected because at least one of those five colors appears in every flag in the world.
The rings are five interlocking rings, colored blue, yellow, black, green, and red on a white field, known as the "Olympic rings". The symbol was originally created in 1913 by Coubertin. He appears to have intended the rings to represent the five continents: Europe, Asia, Africa, America, and Oceania. According to Coubertin, the colors of the rings together with the white of the background included the colors composing every competing nation's flag at the time. Upon its initial introduction, Coubertin stated the following in the August 1913 edition of Olympique:?
The six colors [including the flag's white background] combined in this way reproduce the colors of every country without exception. The blue and yellow of Sweden, the blue and white of Greece, the tricolor flags of France, the United Kingdom, the United States, Germany, Belgium, Italy, and Hungary, and the yellow and red of Spain are included, as are the innovative flags of Brazil and Australia, and those of ancient Japan and modern China. This, truly, is an international emblem.