I believe you will need a macro for that.
As I have never written a VBA macro, here are some quotes from people who have:
From How do I get rid of form field shading in Word? :
If you are using a highlight on the
formfields - which you must have put
before you protected - then you have
to unprotect the document to remove
Dim oFF As FormField
' remove shading
ActiveDocument.FormFields.Shaded = False
If ActiveDocument.ProtectionType = wdAllowOnlyFormFields Then
' remove highlighting
For Each oFF In ActiveDocument.FormFields
oFF.Range.HighlightColorIndex = wdNoHighlight
ActiveDocument.Protect wdAllowOnlyFormFields, NoReset:=True, Password:=""
Some more info from Change the colour that indicates sections that are editable :
There isn't a way to change the
highlight colour used by Word to shade
editable regions. You can
programmatically turn shading of
editable regions off by using the
property and setting it to False.
Of course if you do this, you will
lose the automatic yellow highlighting
that Word provides. You would then
have to write some code to highlight
the ranges by yourself that are
editable in the document, code like:
Some problems with this approach:
1) If the user selects the entire
region and deletes it the gray
background color will be lost.
2) The gray background colors will
print when the document prints, so
you'll have to handle the BeforePrint
event and remove the gray background
colors before it prints.