Nice find! Enjoy your Junior. Vacumatics are outstanding writers and I'm sure this one is no exception.
As for discoloration, this looks like a reasonably clear example. If you can see the breather tube through the barrel you have pretty good transparency. I have examples that run the gamut between "almost clear" to transparent red amber. The silver trim looks nice on this one as well.
Note: Although the plastic color may have "drifted" with age, this looks to be a standard gray model Junior.
Best regards,
Jon