Further to what I wrote yesterday about this, I've written a jQuery plugin to provide a nice interface to pseudo-element CSS changes. Basically it *kind of* allows you to target pseudo-elements for the sake of CSS manipulation. It looks something like this:
$('#element').pseudoCss(':before', 'background-color', 'red');
Please do read the caveat section before you use it. It should work for most situations but it is inherently limited compared to $.css().