Today I added GTK theme colors support to the 1.3.x code in SVN (update: now merged with stable 1.2.3). Now Liferea adapts the HTML rendering to your GTK theme settings. Here is a screenshot when running with a pretty standard ClearLooks theme:
While the same display in some dark theme looks like this:
Of course depending on your themes contrast settings and base color some elements like the blue links in the above screenshots do hurt the eye, but this is something that is hard to avoid. Despite this I think this improvement helps to blend in more with other applications in your GTK/GNOME desktop. Depending on the used theme the old default gray header styles used until now could look "cold" or out of place.
If you have significant problems with the new rendering please send a screenshot of the problem and if possible a link to the theme definition online or at least the name of the theme to the mailing list or post a new item in the bug tracker at SF.