Description of Problem:
If you set your gnome-panel to have a solid color, the clock inherits this
background color for it's background, however, the text of the clock remains
black and there is no way to configure it. This becomes very annoying when the
color of the panel is set to something dark and the clock becomes unreadable,
and mostly indistinguishable except for the white/grey box outline.
Personally I don't think there's a real fix for this (other than
using a dark theme with white text to begin with), which is one reason
colored panels are a somewhat "toy" feature. You can't make one of the
15 or so GTK colors configurable for something without making them all,
which would just be nuts. But probably worth filing on bugzilla.gnome.org
to see if someone has a clever solution.
Upstream as http://bugzilla.gnome.org/show_bug.cgi?id=103288