Fix N3 terminal bg color so it matches GUI color

I think the bg color for the airline gutter isn't correct, as it's different from the GUI.

Screenshot in terminal before and after this change:

![screen shot 2014-01-04 at 5 30 44 pm](https://f.cloud.github.com/assets/1532071/1844819/c509dd08-7555-11e3-9092-3e3bf82a4ef3.png)
![screen shot 2014-01-04 at 5 30 36 pm](https://f.cloud.github.com/assets/1532071/1844820/c50cafec-7555-11e3-9f69-759ce94e4efd.png)