This feature was exclusively part of a joke version and is not currently planned for addition to regular Minecraft. It is documented here on the wiki due to being officially-released content by Mojang Studios, even if not present in a final version.
One le tricolore and one la baguette is given to all players when French mode gets activated. Deactivating the mode will remove le tricolore from the player's inventory (but not la baguette; containers such as chests are not affected).
Le Tricolore is not available in the creative inventory, but can be obtained by using the /give command.