Because, you see, they exist. And they've been to us. And people have seen them. No, not even I buy that... Some general little conception to make them appear more distant from humans, I suppose. More alien, if you will. No one has green skin after all. Pretty good work here, anyway! I do think the complexity of the shiney spot on the hair deters from the rest of the painting's simpicity, though. Stands out. Makes it worse overall. But it's not bad.