Not everything you listed is the same.

> Is "pink" a different colour than (light) red?

No, it's a different word for it.

> Where does "white" end and "grey" begin?

When any amount of black is added to white.

> Where does "grey" end and "black" begin?

When the color is 100% black.

White and black are not the same as red, green, or blue. Tinting or shading a color with white or black does not change the color, it lightens or darkens it. That's not the same for RGB. Combining those results in other colors, regardless if a culture has a specific name for it.

>> Where does "grey" end and "black" begin? >When the color is 100% black.

But what does this mean? Only vantablack is black, everything else is grey?