The Study of flags is called Vexillology and the person who studies it is called a Vexillologist.
There are six colours on the flag of South Africa : Red, White, Black, Gold, Green and Blue. It is the only nation to use six colours in the primary design of the flag.
The 27 stars in the Brazilian flag represents the 27 states and it depicts the same pattern that was visible in the night sky of Rio de Janeiro on 15 November 1889, the day Brazil became an independent republic.
Libya is the only country to have a flag with a single colour, a solid green.
The Ashok Chakra(wheel of duty) in the Indian flag represents the righteousness, progress and perpetuity. The 24 spokes of the wheel represents the 24 hours of a day.
Southern Cross Constellation, which is the brightest in the southern skies, appear on the flags of Australia, Federated States of Micronesia, New Zealand, Papua New Guinea, Samoa, and Solomon Islands.
The flag of Chile can only be flown with a white pole.
The 13 stripes in the US flag represents the original 13 states of the Union and 50 stars represents the number of states today.
The red colour appears on about 75 percent of the flags around the world.