Blue Flame

In Ocarina of Time, Blue Fire can be found free of charge in Ice Cavern and Ganon's Castle, or for 300 Rupees at the Medicine Shop in Hyrule's Market as a child or Kakariko Village as an adult for 300 Rupees. Additionally, Blue Fire can also be found in Master Quest's version of the Gerudo's Training Ground.

In any case, an Empty Bottle is needed to store Blue Fire. The only function of the uniquely-colored fire is to melt Red Ice.

Spirit Tracks also features blue fire, but it is an object, not an item. It "burns" the boomerang and can be used to freeze water.

Trivia

 * When Keese fly through Blue Fire, they become Ice Keese.
 * The Blue Candle from The Legend of Zelda is similar in appearance to Blue Fire, but the two items are very different in function.
 * In the book "Harry Potter and the Philosopher's Stone" by J. K. Rowling, there is a spell which create a blue fire that can be stored in a bottle.