Originally Posted by Mel!
White Balsamic vinegar comes from green grapes and red Balsamic vinegar comes from purple grapes.
Not true - even purple grapes produce a white juice. ALL grapes produce a white juice. The color comes from how long the juice stays with the skin. The skin of the grape is what produces the color. For example...a rosé wine is just bled off of the barrels (or vats) of wine. Garnache is a red wine, but, you can make a rosé wine by bleeding off before it turns red.
But, back to vinegar. The trebbiano grape is the variety used most often and it is a white grape. The color of a balsamic vinegar comes from boiling down the juice, caramelizing. If I recall, the juice (once boiled down into a syrup) is put into a barrel, as it reduces through evaporation it gets put into smaller and smaller barrels over time and the barrels can be different woods, giving the vinegar layers of character.