Is this like a purple cow?

I learned a new phrase today from a visiting scholar from Argentina. We were discussing a colleague and he described her as a perro verde, or green dog. This is used to indicate someone who is unusual or rare, either good or bad. Maybe more bad, but he’s too nice to say that. Since dogs are rarely green, people who are perros verdes are uncommon in their personality, work ethic or style. I can’t explain why I like this expression so much (perhaps it is the image of the Benji dog in my head covered in hair the shade of green food coloring), but I’m going to introduce it into my personal lexicon.