Fix topic list colors: copy from mobile, only define once

The first diff is copied from the mobile topic-list.css.

![image](https://cloud.githubusercontent.com/assets/627891/2979664/9a7ce488-dbd3-11e3-8cae-b9df83a8f5da.png)
![image](https://cloud.githubusercontent.com/assets/627891/2979671/baaa9278-dbd3-11e3-8471-ec4976e1f595.png)
![image](https://cloud.githubusercontent.com/assets/627891/2979665/a31c4412-dbd3-11e3-8bad-8a6928e29b95.png)
![image](https://cloud.githubusercontent.com/assets/627891/2979667/b0e0198e-dbd3-11e3-9db5-f1e85cf4a314.png)