[MassHistPres] Appropriateness question

[Ward Hamilton at Olde Mohawk Masonry & Historic Restoration]

An "appropriateness" question: An unnamed Second Empire residential
structure has
its original, polychromatic Vermont slated mansard (ca 1861.) Structure is
individually listed on the NRHP, in the federal historic district and is
in the
local historic district.

The owner wants to restore the cornice, box gutters, dormers, etc., in
kind.  One
problem:  He wants to replace the old slate (which must go) with new black
slate. A
presentation to the Historic District Commission in early April is planned.

How does he articulate this? We're replacing slate with slate, but
monochromatic
black. It is reversible, and "does no damage." I realize this isn't
optimum--I wish
he'd replicate the Vermont slate color scheme. But he doesn't want to.  Thank
goodness he wants to revive this otherwise-abandoned landmark.

Your thoughts appreciated. Thanks.

Ward Hamilton