The colors were chosen to be blue, yellow, black, green, and red, because every national flag in the world has at least one of these colors.
These five intertwined rings represent the unity of the five inhabited continents (America, Europe, Africa, Asia, Oceania).
Had NO Clue! 
Pretty! This has been an incredibly wonderful article – Olympics Flag: Why 5 rings? Why those colors? Had NO Clue!. Many thanks for supplying these details.