Blue

Black vinegar is dark-colored vinegar traditionally used in Chinese and other East Asian cuisine. One of the most important types of Chinese "black vinegar" is the Shanxi mature vinegar from the central plains of Northern China, particularly in the Shanxi province (Shanxi mature vinegar). It is made from sorghum, peas, barley, bran and chaff and has a much stronger smoky flavor than rice-based black vinegar. It is popular in the north of China as a dipping sauce, particularly for dumplings.[citation needed] Another type of Chinese "black vinegar" is Zhenjiang vinegar (simplified Chinese: 镇江香醋; traditional Chinese: 鎭江香醋; pinyin: zhènjiāng xiāngcù) and similar condiments from southern China. The condiment is an inky-black rice vinegar aged for a malty, woody, and smoky flavor. It is made from rice (usually glutinous), or sorghum, or in some combination of those, sometimes including wheat and millet. Black vinegar was traditionally aged in clay pots.

Source: Wikipedia