Lightens the background color of detail messages

Before:
![screen shot 2014-12-11 at 5 25 51 pm](https://cloud.githubusercontent.com/assets/186715/5405530/ea4e47fe-815a-11e4-9b15-aaff22ec80dd.png)

After:
![screen shot 2014-12-11 at 5 25 06 pm](https://cloud.githubusercontent.com/assets/186715/5405532/ed1be982-815a-11e4-8f9b-50137fecf861.png)