[Serna] formatting gets lost when switching to markup view

Hello,  I am a new user of Syntext Serna.  I have created a xsl fo
 stylesheet to customise the look for my documents.  Among other
 things, I have added background colours to a number of elements.  When
 switching to markup view where all element tags are displayed, the
 background colours disappear.

 How can I avoid this?  It is really helpful to see the background
 colours.  Thanks in advance.

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 cheers,
 Jakob.

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-- 
cheers,
Jakob.