fix(variables): darken text input color

before
![image](https://cloud.githubusercontent.com/assets/399776/5385701/9a377902-8079-11e4-8324-e90cf7d014d7.png)

after
![image](https://cloud.githubusercontent.com/assets/399776/5385693/8604c732-8079-11e4-9944-f757b968f94a.png)