Answer:  Magenta. 

 

It was named for the Battle of Magenta, which was fought in 1859 near the town of Magenta in northern Italy during the Franco-Piedmontese war against Austria.  The deep purplish color – on of the first dyes – was discovered soon after the battle and was named to commemorate it.

 

Source:  The 365 amazing trivia facts calendar 2007.