adjust tones on list items

Reverses listing background color in source/style modes:

![screen shot 2014-05-21 at 1 35 53 pm](https://cloud.githubusercontent.com/assets/108094/3044119/73f7068c-e10e-11e3-9fe4-7b08ae981c75.png)
![screen shot 2014-05-21 at 1 36 05 pm](https://cloud.githubusercontent.com/assets/108094/3044120/73f7dd8c-e10e-11e3-9efa-eaa34bc36a8c.png)