Ruppy the transgenic puppy at 10 days old. Even under natural light the red protein can be seen in the skin and fur. The next image shows Ruppy under ultraviolet light (Photo: Byeong Chun Lee)

Ruppy the transgenic puppy at 10 days old under ultraviolet light, showing the red fluorescent protein produced by sea anemones (Photo: Byeong Chun Lee). 

Ruppy's puppys. The ones on the ends have the RFP gene, while the one in the centre does not. Ruppy was bred to a non-transgenic dog, and fluroescent puppies were born in the expected Mendelian ratio. (source: New Scientist)