Similar cases
While these instances are incredibly rare and have little evidence of them online, it doesn’t mean it has not happened before and all over the world as well. Back in 2014, in a completely different part of the earth, two green puppies were reportedly born with green fur, just like Forest.
Recently in a different part of the United Kingdom, a labrador gave birth to a little green puppy as well. Maybe there is something in the water over there in the UK, who knows, we are just glad the little guys are safe. Could it be that this green color is not as rare as we think?