Possibly .... but they still have their protective covers on them, and have been in an unopened sleeve for years. I mean if you put them against a dark background, yes they look white ... but compared to a sheet of white paper ... they definitely look Ivory.
Just did a little test ... peeled up some of the protective film, it is decidedly "tan/ivory" colored ... so no real way to tell without applying them first. The back side of the actual letters looks quite a bit whiter than the side that shows through the protective film. The film is a wax paper like product ... and has the brown paper bag tint to it.
I think you are right, the letters are probably a whole lot whiter when applied to a vehicle than they look inside their protective film.
Someone with more money than me take an NOS sticker and open it up and stick it to something