Denny Anspach said:

The issue of whether any given color photograph may be an accurate mirror
of color is a judgment that almost always has to be made contemporaneously.
Even then, even though judged acceptable, truly accurate matching has to
be rare. I strongly suspect that Tony Thompson's original SP color
photos were left unused and untouched (or almost so) serendipitously in a
cool black file drawer for the next 50 years- another rare circumstance in
any event.

All true, Denny, but those SP transparencies certainly were used for
publicity, at least when they were new. That they may then have been stored
properly attests to what any archivist will tell you: color transparency
film is quite reasonably stable, IF and only IF it is stored properly.
That there may have been some minor shifts in color in the last 60 years
is of course true. The same would be true if the same photos were taken on
the same day at noon and 5 PM. I well realize that color photos are only a
starting point.

Tony Thompson Editor, Signature Press, Berkeley, CA
2942 Linden Ave., Berkeley, CA 94705 http://www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@signaturepress.com
Publishers of books on railroads and on Western history