Most goldfish are born black/brownish. That 's because their mommas will eat them if they can find them, so being in camouflage is a survival tool. Most of the fry turn orange/yellow, but some stay black/brown. When you see tanks and tanks of gold goldfish in the store you are seeing them with the dark ones culled out.
After your fish spawn for a few years, you may find that the surviving babies, now grown up, are black/brownish, so,you may want to start over again. But, if you have named your babies and have become best buddies, and want to stay in contact, give them to a friend or relative.