Pony Thought of the Day: It's Finally Come to This

Yeah, we've deteriorated to the point where I'm just posting a picture someone drew of myself as a pony.

Picture by Viga

I would actually prefer to be an Earth pony, but she said it was too awkward to draw me holding the book, so she gave me a horn. My magic would totally be gray, though.

In fact, yes, let's make this a poll/question/thingy post: If you were a unicorn, what color would your magic be? Why?