I talked with James pfarr about the genetics behind silver vs. yellow and he thinks they're just a dilute form of YG's So to have a silver you'd need to either breed to another silver or a YG carrying the dilute gene.
Yes the darkthroat, cinnamon, yellow, and splash goldens are all documented to have come out of pure birds. The peach, flame, and silver are all unknown but since the silver golden mutated out of yellow goldens they're a safe bet.