更改ViewController Swift的背景颜色？ （单视图应用程序）

I am making a very simple single view application in Swift (XCode 6.2) that comprises of 2 buttons "blackButton" and "whiteButton". Upon clicking blackButton it changes the View's background color to Black and upon clicking the whiteButton it changes the background to white. Can anyone suggest any possible ways to do this? I am making a very simple single view applicati