The old high low face gambit

[Harry Putnam <reader@newsguy.com>]

How can I get finer granularity than just `high' face and `low' face
on the basis of scoring?

I mean something like a face for scores of 1, different for 5, different
yet above 10 etc.  (I have the default score set to 1)

I'm thinking about using procmail to add something to incoming
messages of choice that gnus can score on.  Maybe an assortment like:

   X-Score-Line: NUMBER
Where formail/procmail sets NUMBER according to my recipe.

And set up scoring to read the NUMBER and color the summary buffer
accordingly.  I don't really know how to do that part either but
pretty sure it can be done.  Even if by adding X-Score-Line to xtra
headers. 

But I don't see a handy way to invoke any other faces than low and
high.