What colour does black hot tea turn when vinegar is added to it?

Here's why:

* Vinegar is acidic. While it can react with certain substances to change their color, it doesn't react with the pigments in black tea in a way that would make them change color.

* Black tea is already a dark brown/black color. The pigments in black tea are quite stable and don't easily change color.

You might notice some slight changes in the tea's taste or aroma when vinegar is added, but not its color.