Tomato sauce can go bad even if it is not past its expiration date. Generally, it can last five to seven days when refrigerated or frozen. It will not go well if left out for more than two hours in temperatures above 40F or one hour above 90F. High temperatures are a breeding ground for bacteria and mold.
Therefore, you should never leave the sauce out longer than it has to be. You can’t tell if tomato sauce is bad by looking at the color. It’s most likely spoiled.