One time we had a road show, a marketing event providing technical seminars, in Beijing. After the event, our Chinese colleague was so nice to bring us around including the Olympic venue when China hosted it in 2008 and the famous Great Wall of China.
We had the chance to walk a portion of the Great Wall which was swarming with tourists. It was exhausting I found out.
In 2008, China hosted the Olympics in Beijing. We visited some of the venues which they maintained for tourism I guess.
The rings are colored and only yesterday I got to know the colors stood for the continents, although it has not been used by the Olympics for reason that I don't know.
Black = Africa
Red = America
Blue = Europe
Yellow = Asia
Green = Australia/Oceania