Red letter day on the red carpet

The 82^nd Oscar Awards Ceremony took place last night on
Hollywood Boulevard, five minutes from my home in Los Angeles. As is the custom
every year, the guests made their way to their seats by crossing a red carpet.

This custom is inspired by the English
expressions: “to roll out the red carpet” ("dérouler le tapis rouge")
or “to give someone red-carpet treatment.”
One definition of red carpet given by Webster’s New World College Dictionary is
“a very grand or impressive welcome and entertainment” and “to roll out the red
carpet” as “to welcome and entertain in a grand and impressive style”.

Other expressions and idioms contain the word “red”:

• 
  Like a red rag to a bull. (voir rouge) This denotes
  any words or actions which infuriate someone. e.g. When he was reminded of his criminal record, it was like a red rag to a
  bull. The origin of the term red rag dates to the late 17^th
  century. It first denoted a tongue. The Classical
  Dictionary of the Vulgar Tongue, 1785 contains the following
  quotation: "Shut your potato trap, and give your red rag a holiday."
  (The expression shut your trap is
  still used in “vulgar” speech today.)

A related expression is to
see red, meaning to become enraged.

• A red letter day (un jour à marquer d'une pierre blanche) refers to a significant day. The term
  originates in church lore and became popular with the appearance in 1549 of the
  first Book of Common Prayer in which the calendar
  showed special holy days in red ink. Red letter days were days for rejoicing
  and celebration.  

• To raise a red flag (signaler une alerte rouge) means to alert
  someone to a danger. It is now commonly used in a commercial context, e.g. The sales figures for last month raise a red
  flag.
  

• A red under every bed – (avoir des rouges sous son lit) This expression
  is a vestige of McCarthyism in the USA.  Senator
  Joseph McCarthy (1908-1957) led a witch-hunt from the late 1940s to the late
  1950s against anyone suspected of belonging to the Communist Party. The
  Communists were known as “Reds”, on account of the color of the Communist Flag.
  The expression a red under every bed denoted
  the widespread atmosphere of suspicion that McCarthyism engendered.
  

• To paint the town red (faire la fête) means to
  celebrate with much festivity and merriment.

•  Red tape (paperasserie, bueaucratie) denotes excessive bureaucracy or
  an exaggerated reliance on rules. To cut the red tape means to overcome those
  bureaucratic obstacles.

• To catch someone red-handed (prendre quelqu'un la main dans le sac) means to catch someone
  while he/she is committing a crime or a misdeed, or has just committed one (flagrans crimen). 
  The metaphor is that of a murderer caught with blood on his
  hands.