I use green and pink peppercorns (the pink ones aren't actually peppers, but so what) for sauces all the time. The green ones are the same thing as black, just milder.
You can brine dried green or pink peppercorns in salted, water to refresh them. It takes an hour or two before they're soft enough to use whole. Doesn't work with black pepper, the hull comes off the corns, and the corns don't taste good.
I've had fresh green peppercorns in Thai, Malaysian and Indian food. At the end of the day they're just green peppercorns, but a bit more so. More intense, and a little more fruity.
Green, pink or black, if the pepper berries are fresh enough you can simply do your best to clean them, then throw them in whatever it is you're making. Do a small trial sauce first to find out how hot they are before serving to other people.