Black tea refers to the visible degree of oxidation of the tea leaves
Makes sense
grapes are called that because they produce white (clear) liquid
Even if it produced indisputably white liquid. Why not call it after its own color while tea is named after the color of its processed leaves?
You’d expect tea which is thought of as a drink to be known for the color of the liquid, and grapes often eaten as is to be named after their color.
But it doesn’t really matter, any of these could’ve been named after whichever color they were at any point of their making / preparation. It’s not like there’s a convention or something



There is no way that’s true