There is no real relationship between dyestuffs and glass colorants. Dyes are organic compounds; and glasses are colored with elemental mineral oxides.

It is true that most purple glass looks muddy. It must be very difficult to formulate a good purple colorant. However, it has been done. About sixteen (16) years ago I examined a fragment of a Chinese beadwork piece that was amazing, on two counts. 1) It included rich beautiful purple beads, of a tone I had never seen previously nor since then; and 2) ALL of these beads were tiny handmade wound glass beads. I was astounded.

So, it's possible to make a decent purple, and in recent years the colors of seedbeads have improved. (Every time I see new purple seedbeads, I buy thm.)

Regarding pearls, I suspect that colors (nowadays) mostly result from dying white or off-white pearls. If you cannot find a color you like, you could try to dye them yourself. I dye cords for stringing beads quite often. Or I over-dye an existing color. Without some practical experience, I could not predict the result of dying pearls. But it's worth a try—because we know it's possible.