The island is a French possession, and therefore uses the flag of France.
The French national flag - the tricolore - consists of three vertical bands of equal width, displaying the country's national colors: blue, white and red. The blue band is positioned nearest the flag-staff, the white in the middle, and the red on the outside.
Red, white and blue have come to represent liberty, equality and fraternity - the ideals of the French Revolution. Blue and red are also the time-honored colors of Paris, while white is the color of the Royal House of Bourbon.