Actually the natural fish is silver to black. They're a white form of the black skirt. And erm, I'm guessing a hard sell in their white state (so why breed them I wonder). There used to be a local chain that carried them dyed blue and purple. The purple ones were called <gack> Purple Rain tetras. Can't remember what fantastical name the blue ones were called. Man, if you want a colorful fish, there are tons of livebearers and dwarf cichlids that fill the bill.
My mind is aglow with trancient nodes of thought, careening through a cosmic vapor of invention - Hedley Lamar