Change style of matrix row column headers

When using the "Matrix Row" topic format, the column headers are too small and there is no apparent way to apply styling to them. 

Clicking on the topic displays a "Topic Format" page allowing to style only the main topic text.  Clicking on the row headers, which are actual topics allows to style them, but the column headers have no associated format page.

Is there a workaround to style the column headers?