Getting parts of a stylevar?
 

I've got a bbcode that wraps text in a <span> with a class that has its color style set to same color as the postbit background, hiding it until it's highlighted. Right now, the color is manually defined in each style's stylesheet, but what I'd like to do instead is grab the background color value from the postbit background stylevar. I've seen this done before for font stylevars in the stylesheet (e.g. "font-size: {vb:stylevar postbit_font.fontSize};"), and I'm wondering how to do this with the background stylevars? I've tried postbit_background.color, .backColor, .backgroundColor, and just for the hell of it, .fontColor, but with no results.