According to

http://marble.kde.org/kml-guide.php

we support parsing the ListStyle tag from

https://developers.google.com/kml/documentation/kmlreference?hl=de#liststyle

• Copy and paste the 60-80 line example code into a new file and save it with a file name that has the .kml extension
• Start Marble and enable the "File View" panel. Settings -> Panel -> Files
• Load the example code into Marble and check whether the ListStyle changes specified in the KML file are applied to the "File View" panel.
• Create source code which implements the bgColor part of the example:

  <Style id="bgColorExample">

• Check whether it makes sense to add the same capability to the Tour panel. If possible add it to both in a generic way.