[MassHistPres] Second appropriateness question

[Ward Hamilton at Olde Mohawk Masonry & Historic Restoration]

Same building owner, different structure.  Home is a contributing
structure in a National Register historic district and in a local historic
district.  Greek Revival, portico not original, added in 2002.  Historic
district commission (and local historic district) created two years later.
 Portico roof has silver aluminum standing seam that owner wants to
replace with black standing seam.  The non-original portico falls under
the purview of the HDC, but its not original, so what rules guide the
decision here?  [picture attached]
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