Theming issue

[John Ames]

I've got Linux MintPPC running XFCE, and everything's pretty well 
configured to my tastes. Except for one thing: somehow or other, a 
number of the color/theme settings from Mint's default LXDE theme are 
still bleeding through, no matter what theme I set XFCE to use. 
Specifically, the panels, the menus in all applications, and the widgets 
in some applications (Synaptic, for one) all appear as if in the default 
Mint theme. (This applies to the widget appearances as well as colors. 
Other applications, like Iceweasel/Icedove, will happily use whatever 
theme I select.)

Since I prefer lighter themes while the Mint theme is predominantly 
dark, this is ugly and uncomfortable - and it irritates me on principle 
that I can't change things to look how I want them to look. But I've 
tried a number of different things to resolve the issue, including using 
the LXDE configurators (does nothing) and removing Mint's default 
desktop environment and theme files altogether (still nothing.) 
gnome-color-chooser at least let me get the majority of colors the way I 
want them, but the panels and menus are still stuck, and Synaptic still 
thinks it's night out.

Am I missing something here? I'd think the widget thing might point to a 
specific toolkit that's a problem, except for the menus and panels 
exhibiting the same basic problem in every application...