Here is an area of Bengalese Finch keeping and breeding of which I have limited knowledge, in 1999
Mr F. Panjer in the Netherlands imported pearls from Japan and the following year myself  and 2 other fanciers visited him where I purchased a pair of Chocolate Pearls from him.
These being a new colour to me I went all out in breeding, pairing them to my Black Browns and  fostering as many clutches as I could ready for the following season when I aimed to begin developing them for exhibition.
My records tell me I produced 5 Pearl hens and 2 2 other Black Brown birds some split for Pearl. a good start for the following season, but fate intervened and a fancier made me an offer I couldn't refuse so my venture into the Pearl mutation started and finished in the same year.
There are 2 varieties of the Pearl, the Chocolate and the Grey it is a sex linked colour and follows the same mode of inheritance as the Cremino.
I placed an article HERE which will tell you about the introduction of the Pearl to Europe and something of its breeding.