Only weekend (Saturday and Sunday) has enabled background color

Hello :)
When flag of work_on_weekends is TRUE, Background color is applied in all days.
Please see image below.  
![bug](https://f.cloud.github.com/assets/1174586/1208200/640b67ae-25ca-11e3-9a2e-3e8da4e49f80.png)

Only weekend (Saturday and Sunday) has enabled background color.
At the same time, also when flag of work_on_weekends is FALSE, fix a condition.