Qatar's flag owes its color to a dye that could not survive the sun. Take the plain red banner common across the Arabian Peninsula, leave it out in Gulf light long enough, and the red darkens toward the deep brown-red now specified as Qatar maroon.
From red to maroon
Like most of the Gulf sheikhdoms, Qatar flew plain red. A white field was added in the 19th century, at first roughly square, to tell the flag apart from its neighbors, and a treaty with the British in the 1800s required the white stripe. What no treaty specified was the shade. The dyes faded, the red drifted darker, and the resulting maroon became Qatar's own. It also settled the question of confusion with Bahrain, whose flag stayed bright red.
The maroon and white flag with the serrated division was adopted on July 9, 1971, weeks before independence from Britain on September 3. Nothing about it has changed since.
Nine points and a treaty
The number of points on the serrated line matters. There are nine, and they mark Qatar as the ninth member of the reconciled emirates of the Persian Gulf under the Qatari-British treaty concluded in 1916. Maroon is read as the blood shed in Qatar's wars, white as peace.
The proportions are unusual as well: 11:28, much longer relative to its height than most national flags.
Flying it
The flag flies at government buildings and military bases, and schools are required to display it. Protocol covers handling, position relative to other flags at international gatherings, and flying at half-mast during national mourning. Military and naval variants add branch emblems.
It comes out in force for Qatar National Day on December 18, and it travels to the FIFA World Cup, the Olympic Games, and diplomatic summits.
Qatar and Bahrain
The comparison is unavoidable. Both flags divide a colored field from a white one with a serrated line, a shared inheritance of British treaties in the Gulf. Bahrain's is bright red with five points; Qatar's is maroon with nine. Elsewhere in the region flags tend toward plain tricolors or emblems, which leaves the serration to these two.
References
[1] Qatar Ministry of Foreign Affairs: www.mofa.gov.qa
[2] Vexillology Associations: International Federation of Vexillological Associations
[3] Qatar National Library Historical Archives