A red carpet is traditionally used to mark the route taken by heads of state on ceremonial and formal occasions, and has in recent decades been extended to use by VIPs and celebrities at formal events.
More generally "red carpet treatment" and "rolling out the red carpet", refer to any special efforts made in the interests of hospitality.
The earliest known reference to walking a red carpet in literature is in the play Agamemnon by Aeschylus, written in 458 BC. When the title character returns from Troy, he is greeted by his vengeful wife Clytemnestra who offers him a red path to walk upon:
"Now my beloved, step down from your chariot, and let not your foot, my lord, touch the Earth. Servants, let there be spread before the house he never expected to see, where Justice leads him in, a crimson path."
Agamemnon, knowing that only gods walk on such luxury, responds with trepidation:
"I am a mortal, a man; I cannot trample upon these tinted splendors without fear thrown in my path."
Oriental carpets in Renaissance painting often show rugs and carpets, patterned but with red often the main background colour, laid on the steps to a throne, or on a dais where rulers or sacred figures are placed.
A red carpet was rolled out to a river to welcome the arrival of United States president James Madison in 1821. In 1902, The New York Central Railroad used plush crimson carpets to direct people as they boarded their 20th Century Limited passenger train. This is believed to be the origin of the phrase "red-carpet treatment". Film premieres are often laid down with red carpets.
Unrolled carpets can be potentially hazardous. In 2010, when Pope Benedict XVI arrived at Edinburgh airport in strong winds for a state visit to Britain, the red carpet was removed on health and safety grounds.
Publicity events 
A red carpet is also used in gala celebrity events such as the Academy Awards, Met Ball and Baftas. Whilst the awards take place inside, much of the publicity and excitement takes place outside with journalists discussing the red carpet fashions, what designers are being worn by which stars and photographers taking pictures. This is now a spectacular international product placement arena of great importance to the fashion industry. Red carpets are often coupled with publicity backdrops which contain brand logos or emblems for photography purposes.
Carpeting in other colors may replace red in some instances to honor a certain cause or for a sponsored event, the sponsor's logo colors, such as a "green carpet" to promote environmental awareness, or for the Nickelodeon Kids' Choice Awards, an orange carpet is used instead to go with the network's primary imaging color.
Red carpets are now also used at non-royalty or celebrity events such as weddings.
United Airlines operates a series of VIP Lounges at major airports that were formerly known as "Red Carpet Clubs".
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- "How did "red carpet" come to be synonymous with royal treatment?". Ask Yahoo. 2005-09-16. Retrieved 2008-03-09.
- BBC TV News, 16 September 2010