Purple LED lights! (or are they?)

I'd wanted them for a couple of years, and finally I found a local source for PURPLE LED fairy (faerie? feri?? no.) lights, and hooboy was I happy! Yay! Purple LED lights, no shipping! As soon as I got home I strung them up.

 

But- wait! I know one or two things about semiconductor physics and engineering -- and there's NO SUCH THING as a purple LED! What's going on?!

Done