[zvr]

But this doesn't really work in long emails and threads.

Scroll a couple of screens in the message text and you see something like:

    > > > > I think that ...
    > > No, I remember that ...
    > On the contrary, I believe that ...

(maybe with different colors) but you have to remember the stack/colors to decipher who is saying what.

Unfortunately I have not seen mutt coloring the index with the same colors as the quoted text, which would help a lot (if you have a view that shows the index along with the message).