If you think you will study the history of the breed, I think you will find
at one time or another that both the tri and the blue were held in low regard
and almost threatened with extinction by the dominating sables.  In those
instances, an informal or, in one case, a formal organized group gathered to
preserve them and with their efforts obtained an end to discrimination against
them by judges.

Combined efforts put the coat back on the tricolors, that had so far fallen
behind the sables until now most tris are a heavy or heavier in coat than their
sable contemporaries.  Likewise the quality of the blues in head was improved
immeasurably at one stage.  So it appears that if there is a sufficient group
interested in whites, there is no reason why they cannot take stock and working
together make any improvement needed and at the same time publicize the color
enough to improve their chances in the ring.

Why be horrified at mating white to white?
Understand both the sable and white and the white with sable markings are
classified as 'piebald" generically.  If there is no albino involved, why should there
be any more worry about mating one or more of the above.

While it is possible that white to white would in time lose
the sable heads via the blaze route, that could be remedied by occasional
return to a plain-faced sable line.  However, I do not think it would be
insurmountably difficult to obtain a larger proportion of whites.  Certainly I
would not be frightened out of mating white to white by albinism,
if I were sure of my dogs' background.
The following article is from the book
The Complete Collie
by Milo G. Denlinger
3rd Edition, New Material, 1949
" More Notes On Breeding Whites "
by Oren Kem, Lodestone Kennels, USA