From the University of Hawaiii:
The green color simply indicates that the fluorescent genetic material injected into the pig embryos has been incorporated into the animal’s natural make-up. “It’s just a marker to show that we can take a gene that was not originally present in the animal and now exists in it,” explains Dr. Stefan Moisyadi, a veteran bioscientist with the IBR.
Dr. Moisyadi said the animals are not affected by the fluorescent protein and will have the same life span as other pigs. “The green is only a marker to show that it’s working easily,” he said.
The ultimate goal is to introduce beneficial genes into larger animals to create less costly and more efficient medicines. “[For] patients who suffer from hemophilia and they need the blood-clotting enzymes in their blood, we can make those enzymes a lot cheaper in animals rather than a factory that will cost millions of dollars to build,” Dr. Moisyadi said.
And look how cute they are!