Absinthe

Absinthe is an anise-flavored liquor or spirit that is made by steeping wormwood and other aromatic herbs (e.g., hyssop, lemon balm, and angelica) in [[alcohol. The liquor is a dazzling emerald blue-green color, due to its chlorophyll content, and is normally clear.  It changes to a cloudy white when mixed with water.

For further reference

 * http://whatscookingamerica.net/History/Absinthe.htm