Which is the rarest color on national flags ??

  Only two nations out of 196 nations in the world has this colour on their flags   !!!

The colour is     PURPLE .

Only Nicaragua anf Dominica are the nations which are using this colour on their flags.

Purple dye which is used to make purple colour is very costly. 

Purple dye is derived from a sea snail which is present in limited areas. 

Also, making purple dye is labour intensive and take more than 10000 sea snails to make one gram of dye  !!!

The cost of using purple dye on national flags is very high making it rarest colour on national flags .