You pretty much need some kind of layer control in any case to distinguish existing vs demo vs new - whether multiple layers in the same file (what I've generally done - although layer bloat is annoying) or via hotlinked files (Eric Bobrow's approach, discussed in other threads).
So, given layer control, you can easily have a separate view for 'existing'. Simply assign the drawing created from that view a different pen set, and stack it with your other view(s).
If you'd rather display all elements in a single view, then it requires some specific pen assignments in your pen table so that you use certain pens for existing things that will be mapped to gray (etc) in the pen set used for printing.
Cheers,
Karl
One of the forum moderators
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