Clay Loveless, spurred on by a comment from a visitor to his site, has modified his Trac package to get things working correctly with the syntax highlighting.
As John Herren pointed out in the comments to yesterday’s post, my suggestion for PHP syntax coloring wasn’t working for several versions of Trac.
After a little digging, it turned out that my CSS rules were based on the non-standard SilverCity highlighting output, rather than the newer and more common native PHP highlighting.
His solution is to create a simple shell script, php_mimeview, to make adding cirrect syntax highlighting as easy as changing your config.