You should be able to do it within your plugin. What have you tried?
Custom CSS/JS access to theme/skin colors
While using less in the custom CSS, is it possible to gain access to the colors used in the theme/skin (specifically the skin).
I'm trying to plop in a background image floating underneath the content but allowing users to change skins causes problems because the main content area is transparent. So either I can set it to something light, which messes up dark skins, or set it to something dark, which messes up light skins.
Ideally, I'd like to transplant the body background color to the #content div without modifying the theme or skins.
oof... maybe, but not yet, I don't think.
We can use LESS insomuch that what is entered is parsed back out into CSS, but because we don't rerun "variables.less" from bootstrap, then you can't really use variables.
I'd recommend opening up an issue in our bug tracker so we can get this in if it's something you want