Show num and heading slightly separately in show-structure

[goose-life]

Even when doing a simple structure check of a document, one must still enter Edit mode to check if num and heading have been captured separately (they haven't in this case, the - between the two is missing)

Without adding too much clutter, it would be great if there could be a slight distinction between the two elements: maybe different shades of the hier colour, in this case the section minty green? or only shade the num, so that it's obvious if the heading has been included?

[longhotsummer]

Our XSL doesn't allow this at the moment, because the num and the heading are merged into one heading element, such as

<h2>Chapter 1<br>Founding provisions</h2>