purple strings

[A440A@aol.com]

Greetings all,

      Does anybody have an idea as to what would make a complete set of bass
strings turn the most beautiful, dark purple?  The set is only two or three
years old.
     The color is so even, I must assume it was in the air, as there are no
splash marks etc.  the piano is in a college dorm, though it is not,
(surprisingly!) trashed.

Thanks,
Ed Foote