"The rings were composed of five interlocking rings, coloured blue, yellow, black, green, and red on a white field, known as the 'Olympic rings'. The symbol was originally designed in 1912 by Baron Pierre de Coubertin, co-founder of the modern Olympic Games. According to Coubertin, the ring colors with the white background stand for those colors that appeared on all the national flags that competed in the Olympic games at that time. Upon its initial introduction, Coubertin stated the following in the August 1912 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 tri-colors of France, England, America, Germany, Belgium, Italy, and Hungary, and the yellow and red of Spain, are placed together with the innovations of Brazil or Australia, with old Japan, and with new China. Here is truly an international symbol.'"

Sources:

Wiki, which cites the quote from Coubertin.

Lennartz, Karl (December 2001 – January 2002). "The Story of the Rings". Journal of Olympic History. 10: 31. Retrieved 7 January 2016. "De plus les six couleurs ainsi combinées reproduisent celles de toutes les nations sans exception. Le bleu et jaune de Suède, le bleu et blanc de Grèce, les tricolores français, anglais, américain, allemand, belge, italien, hongrois, le jaune et rouge d’Espagne voisinent avec les innovations brésilienne ou australienne, avec le vieux Japon et la jeune Chine. Voilà vraiment un emblème international."

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