Fill color default?

This is just something that's been annoying to me lately. I don't know how it happened, but a few months ago, every time I make a new document the default fill color is green. so every time I make a new shape it is green. I'd like it to be no fill by default. I know I can just click the no fill box while nothing is selected to change the default fill for the specific document I'm on. But how do I change it permanently?