DC-Barrel Polarity Tester

I made this project to test the polarity of dc barrel jacks. So that when I add one to a circuit, I can tell that it is wired properly. I made the case out of hotel lotion bottles. It lights up red for center negative and green for center positive. Both lights will be on when it's connected to an AC power source (although technically they're not on at the same time, they are alternating 60 times a second.)