You can add custom CSS to CB using the CSS override feature shown below.
www.joomlapolis.com/blog/kyle/18711-template-css-overrides-made-easy
You'll need to right click and inspect that tab menus HTML for the CSS classes to use in your custom CSS. Example as follows.
Code:
.cb_template .cbCanvasHomeLayoutNav .cbNavBarMenu .cbNavBarLink {
color: red;
}
The above will make inactive tab names red.