As an aside the statement, "To judge from historic photographs, the
original windows were
a light color, perhaps buff, matching the original limestone and
light brick.", a word of caution.

If you know all colors are the same hue (all blues, tans,
whites/blacks/neutrals, etc.), you have some guidance by the values
you can see in historic photographs.  But if you have warm and cool
colors together (blues and tans for example, including warm greys and
cool greys), all bets are off.  Due to the color sensitivities of
historic emulsions on the negative, you can't rely on the lightness
or darkness in the photos.

I have a house with multi-colored glass in the windows.  The dark (to
the eye) looking blue window glass prints from old negatives as very
light, and the light yellow glass prints dark!.  I know the glass did
not change much, and the patterns match up from one window to the
next.  Add to this deviation the complication of shade and shadow,
and a good measure of Murphy's Law: my advise...be careful what you
surmise from photographs regarding original color, you may be reading
a lot of your good taste into the conclusion.

And if someone would only put into print a reliable documentation of
"Traditional photographic emulsions and their representation of color
values", please let me know.  Then I only need to find out the
original emulsion before I take on Murphy.

--The Reverend Jim