Hi,
Cheap limits the options, Free makes them almost non-existent. BUT,

I found free. (Must have OSX)
I've been using this program for several months now..upgrading from versions .5 to .7 to .9. as they come out. It's great and does way more than colorcode your work.
Note: it's not even to version 1 yet...very much beta, but the bugs I've found are never catastrophic. The other caveates are that you will have to build it from source..(was easy to do). Download the .tar.gz or .tar.bz2 along with the MD5 checksum for verification. You'll have to determine which gtk your OSX machine is able to use (hopefully gtk2)..and you might have to install the gtk2, or you may find it's already installed. The make and installation for the program itself was almost done in a literal blink of an eye.
So,

*drumroll*
Blue FishThese are some of the same people as those working on the OpenOffice project.
see ya,