Hal's explanation

The following is quoted from another of Hal's extremely useful e-mails explaining what all this means:

    Taking them in order

        *sequence_unseen: -foreground blue

    That changes my unseen messages back to the way they've always
    been.  I like the color association with the folder labels.

    	*sequence_followup: -foreground white -background black
    	*sequence_reply: -foreground green -background black

    These two are sequences of my own devising.  One for things that
    need some sort of followup action by me and one for messages
    that need a reply.  I use the followup sequence, for example, to
    mark things posted to the exmh mailing lists that I need to look
    into.

        *sequence_selected: -foreground black -background #ececec

    This, as the doc explains, isn't a "real" sequence but is how
    you can change the appearance of selected message(s) in the
    folder toc.

        *sequence_cur: -foreground {violet red} -background white

    "cur" is kind of a real sequence but kind of not.  It's the
    current message.  Again this is how you can change how the
    current message is highlighted in the folder toc.

    *sequences: followup reply urgent mrange drange range moved \
     deleted selected unseen cur

    This last line defines the "precedence" of the highlighting.
    If a message belongs to multiple sequences or "pseudo sequences"
    then the last one listed in this will "win".

    Anyway.  That's a "real life" example of using these things.  In
    addition to the ones defined by me, I use the "urgent" sequence.

    Now that I've got this new stuff I wonder how I lived without it!

    Thanks a BUNCH to Chris G for building this!

And Thanks a BUNCH to Hal for explaining it to us all :)

Oh, and to manipulate the sequences a message belongs to, just select the appropriate label from the new Sequences button located between the Folder Display area and the Folder TOC area.

Happy Sequencing! :)