Digital BW, The Print

Various colors do produce the same grayscale value.  But, using color film,
which records at least as wide a spectral response as B&W film does, can be
converted it to grayscale to give a the full range of grayscale values.  The
spectral response of both films is quite well documented (Provia and Tri-X
in the case of my other post), and it is therefore quite deterministic to
produce a mapping from the information on the color film, as produced by
it's spectral response, to the same spectral response that B&W film does.

What you can not do is the reserve...you can't have a grayscale value and
turn it into a color value, as said above, it could be any of a number of
color values that are equal to that grayscale value.  But, this in no way
mitigates the ability to closely replicate the response of B&W film from the
information on color film.

Austin