I did not dye these myself, they were purchased dyed over 13 years ago.
But I googled it for you and came up with this as a first link.
Pearls are a matural substance and strong dye should affect them. I have been thinking about trying to use a dye I normally use on feathers - they dye both feathers and nails (keratin), and should affect pearls as well.
If I get round to experimenting with it I'll get back to you.
Here's the link.
[link]