Using d3's selection.call()

You can use selection.call() to re-use behavior on multiple selections. Here, I've defined a colorable function which adds a CSS rule and a click behavior to this, then used selection.call(colorable) to invoke it on two different selections. There are two things to note: first, the colorable function is called with the selection as this. Second, you don't lose the ability to access the selection's data in your setters.