the rings in the Olympics logo are yellow, green, blue and black because at least one of those colors are on every flag in the whole world.
5 five rings for five continents
The Five Continents of this world
The Ring of the Olympic Logo signifies the 5 Continents. The bundle of the 5 rings represents unity.
the six continents
it is the five Olympic rings with London 2012 through it
each country that takes part has one colour of its flag on one of the five rings
each of the rings are to stand for one type of sport like blue for swimming, red for track and field, black for fighting etc.
blue, yellow, black, green, and red
four the five fingers of your hands