i think that's the right idea. you write a letter using red
ink when you invite an enemy to a duel.
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http://www.cc.flinders.edu.au/isana/news/news2/colour.html
Colour Taboos!
from INTER-L, NAFSA's email newsgroup,
Don't use a red pen on a sign-up sheet for international
students because in some cultures red ink is only used to
write the names of the dead or those one wishes dead.
Ireland: "salmon" is disliked for some (unspecified) historical reason
[TT: really? is it just that red is disliked because
red means England? ]
Italy: Purple taboo because color used in churches during lent
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Japan: writing in red relates to conscription letters during
WWII (which were called "Akagami" or "red letters", this
probably only still has meaning for older people in Japan);
[TT: it used red paper, not red ink.]
red ink is also used to break up with a boy/girl friend;
[TT: this is probably wrong.]
purple - pornography, but also associated with royalty
[TT: "purple - pornography" is probably wrong.]
(this is obviously not an exact science); purple also not
to be worn at weddings because it is considered to be the
color that fades the fastest, signifying a relationship
that will fade; black, black/white combination - funerals;
Red, gold, silver and purple - happy occasions; red,
red/white - festival colors; yellow with death