YIN can do this, although perhaps not the most convenient for casual
browsing. Though it scrolls nice headers, and coloured text to the
screen. (-: You mentioned colours in your message, so you might have
been thinking of Yin. The command line would be...
YIN <filename> /AP
the /AP switch tells YIN to page "all" messages in the folder to the
screen. The main limitation is that it's basically one direction for
reading (though you can press "b" to go "back" to the top of the
current message).
Other than that, as someone else already suggested, LIST is good.
Really any text viewer should work just fine, as long as it doesn't
mind overlooking a few non-standard ascii characters between messages
(and mere LF characters seperating lines).
Oh YIN, if wanted, is at...
http://www.vex.net/~x/yirx/yarn-utils.html