Adding Custom Styles via UIVars in Universal Studio

I am trying to change the border color of the CSS class "chapterBox.active" using UIVars, but am having trouble finding any documentation on adding custom.

The CSS should look something like:

I would like to do this with an inline styles without having to link to an external style sheet. If only one class can be changed ".ChapterBox.active" is the most important.

Thanks!

Dave