Last modified: 2012-12-19 11:24:00 UTC
The color used by GeSHi for Lisp keywords is light yellow, so rather than being highlighted, they seem to sink into the white background. The color used for parentheses is light green, and it also blends with the background and makes reading anything with non-trivial nesting a pain. As a result, pretty much any piece of code with 8 lines or more looks like someone sprinkled a bunch of variable names all over the page. It would be good, IMHO, to make the yellow as dark as orange and green darker still. Compare with the modern Emacs' Lisp mode, for example, where keywords are purple (which is a pretty dark color) and parentheses are not highlighted at all. It seems to be significantly more readable.
This needs reporting and fixing upstream at http://sourceforge.net/tracker/?group_id=114997&atid=670231 Locally, CSS styles can be overridden using the MediaWiki:Geshi.css page
[Removing RESOLVED LATER as discussed in http://lists.wikimedia.org/pipermail/wikitech-l/2012-November/064240.html . Reopening and setting priority to "Lowest". For future reference, please use either RESOLVED WONTFIX (for issues that will not be fixed), or simply set lowest priority. Thanks a lot!]
