That's not been my experience Peter. Perhaps the Pl-Au you've seen
was melted in a crucible that had been used for melting other alloys,
like yellow gold. Pl-Au becomes contaminated with copper quite
easily. If melted in a clean crucible, it should come up nice and
gray. I've never torch melted it though, that could be the problem.
I've always induction melted it. It comes out BLACK as can be, and
while never polishing up to a real white like silver, it does have a
very bright whitish gray finish. I have seen certain oriental pl-au
alloys that did seem to have a slightly more whitish appearance,
though that could have been plating.