Add orange as the default color for .job-types for custom Job Types

Hey Mike,

As discussed in the old Pull Request I think there should be a default color for the custom Job Types. I went with orange for this. Obviously the CSS for the existing job types will have more specificity so they will override this.

With this applied the frontend and backend will have an orange background colour. 
![job listings wordpress australia wordpress](https://f.cloud.github.com/assets/1377956/635136/5e7600ee-d23a-11e2-9fac-faed25342550.png)

You might think of another way of dealing with this though :grin: