Why does my Zebra Finch look like this?

Ok so about a year ago I got two Zebra Finch's from my friend and they were two of the babies from her original fiches.So one of them, i believe the female, (not POSITIVE what they are), got all her colors, but the male changed very slowly and barely got it's colored beak, so now it's pretty much just black and white!!! Please someone tell me why this is!!!