Magnolia bars are injecting at the moment their div style design directly in the output.
In my opinion all bars should just define a div class.

By that you could design the bars as you like within the page's/site's css.
See http://wiki.magnolia-cms.com/display/MAGNOLIA5/Templating+-+Proposal?focusedCommentId=50792741#comment-50792741

Probably the page editor should inject a css for the bars which do not overwrite the class values, if already defined within the page's css.