[jQuery] How do I combine if statements with changing the CSS of a div? (Example enclosed)

I don't know if I'm doing this right. I want to make it so, if my green box is green, change it blue when you click on it. Whereas, if the box is blue, change it to green. Basically, this is the file so far, just click View Source.

I get the feeling I'm really not doing this right.

Edit: Changed the URL because I'm not comfortable with GitHub's interface.