Change private repo background color on list

Before
![screenshot 2014-09-01 21 44 41](https://cloud.githubusercontent.com/assets/867840/4109779/5ef50eba-31e9-11e4-898d-370af48e4b02.png)

After
![screenshot 2014-09-01 21 46 45](https://cloud.githubusercontent.com/assets/867840/4109780/69228d72-31e9-11e4-8511-cc4bfc50b42a.png)