I realise this is a little late to reply, but another work around is to apply a thin insulation thickness to the pipe. Insulation under the object styles can be assigned a different material.
Never too late to reply. Always add information to a post.
Now that we have 2012 we can add seperate materials to to pipe systems. So problem solved.
I' m using REvit 2011 in my Office, and I found out that using Phases is a good way to apply materials to pipes or ducts, in addition to Object Styles and Insulation Material. Of course this method is very limited, but we do what we can with revit 2011.
I did this render from left to right: EXISTING Phase, DEMOLISHED Phase, TEMPORARY Phase, Object Style for Pipe, and Object Style for Insulation.
Hope this helps someone.
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