Purple sweet potato vinegar is a fruity rose-colored vinegar made from purple sweet potatoes. Use in sauces, stews or for tangy salad dressings. This vinegar is quite acetic so don't try to substitute it for low acid vinegar such as rice wine vinegar. Use it in a bold sauce that uses soy sauce for example.
You'll probably not find this vinegar at your local grocery store but you can purchase it online at The Chef's Shop. See substitutes.