Blue box is a header. So, it should appear only in you define facet name="header", but not "whenever" like you said.
rich-panel-header class redefine the class for header. You can use it if you want to re-define it for the whole page. If you want to change only one particular instance of panel, use headerClass attribute.
General advice: read the documentation or, at least, see the demo:
http://livedemo.exadel.com/richfaces-demo/richfaces/panel.jsf . "Look Customization" tab addresses your question.