Adapt smoother colors for cb.theme.dark

## After
![screen shot 2014-01-22 at 4 33 35 am](https://f.cloud.github.com/assets/949223/1970857/e66f70ce-8316-11e3-8cd3-e3a6b31e0a46.png)

## Before
![screen shot 2014-01-22 at 4 36 10 am](https://f.cloud.github.com/assets/949223/1970852/da8e6846-8316-11e3-8d05-40c1040e82b6.png)