Wines should be matched to the predominant taste of the food, which in many cases is the sauce or gravy rather than the base food itself.
Whenever the sauce becomes the primary flavor in a dish rather than the meat or vegetable base, it is best to pair the wine with the sauce. This is especially true with lighter meats such as chicken or pork that have sauces, butter, or oils that dominate the meat taste.
Thus a savory sauce could be paired with a savory (low acid) red wine such as a Merlot even if the meat is white. An acidic white wine is also acceptable with red meat if the predominant taste of the red meat with its sauce is acidic.
You could also pair an acidic red wine with a white fish or shellfish that had an acidic sauce.