It appears to be an issue with theme css overriding the css for the plugin (plugin css targets the row, themes target the cell, this trumps the row)
my dirty solution was to go to css/frontend.css and change the ‘.highlighted’ selector to ‘.op-overview-row + .highlighted th’. This targets the heading (day) in particular. Of course you could change ‘th’ to ‘*’ to target the whole row.
The added bonus of this change is that it will stop the ‘.highlighted’ selector changing other elements from other plugins/themes/templates that use the selector.
