SP ng 18 lettering

Hi guys I am trying to sort something out to decal my model.
We know the SP official practice was Aluminum lettering until 1946 and greyish white after that.
However the photos of the NG locos all appear to be plain bright white, even in the 40s when it said SP Lines.
Yes a BnW photo is hard to distinctly tell but in the color photos of the post “Lines” era the locos definately look white not Grey.
There are a limited number of decals in 0scale and I already have the san Juan sets of silver and grey lettering. 50 bucks worth.... and no white.
Even a friend if mine that helped restore and steam 18 agrees with me all the photos look white and not silver or grey.
Just cant figure out what color they actually used on the NG. Im planning to do the war years.
If you actually know or believe you have a really good reason one way or the other i would like to hear it.