There are a lot of threads about the purple color. It may have to do with extra electrons bombarding against the glass. I have some power tubes that do this. I don't know if it is the same with rectifiers. A good rectifier can last nearly the life of the equipment. Maybe you can get it tested to make sure that it is not going bad on you.

Now you can chuck it then. The Philco is probably a Sylvania. You won't have any trouble with it.