Question about syntax coloring using an external program

[Fredrik Öhrström]

I would like to invoke an external program to do syntax coloring and
formatting of the source inside an emacs buffer. I have created an elisp
solution using font-lock mode an regexes, but I would like a 100% correct
coloring solution. It suppose it could be implemented in pure elisp, but
for the moment I need to use an external program to do this. The external
program can annotate the source with tags that probably can be used by
emacs to color the source.

However I am at a loss how to actually implement such a round trip in emacs.
I would greatly appreciate any pointers to similar existing solutions or
hints on how to do it!

Many thanks!

//Fredrik