According to Pierre de Coubertin, creator of 5 interlocking rings of Olympic symbol, the colors Blue, Yellow, Black, Green, Red and including white on the background, states the color of each country that participates in Olympic Games. Coubertin stated the following in 1912 Olympic games:
"...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 and America, Germany, Belgium, Italy, Hungary, the yellow and red of Spain next to the novelties of Brazil or Australia, with old Japan, and new China. Here is truly an international symbol."
source:wikipedia