Make inbox discussion icon colour match unread dog-ear

![image](https://f.cloud.github.com/assets/1380991/1369141/bf827ec6-39d7-11e3-8220-a12e86fa0107.png)
![image](https://f.cloud.github.com/assets/1380991/1369142/c5ae787c-39d7-11e3-9306-838e0800e1e8.png)