Football team colour difference

Add logic to better handle team colours on the stats.

* Darkens away team if both teams are the same colour
* darkens teams away from white (so the stats are clear against the background)
* If both teams are white, darkens both but darkens away team more so they are clearly different

Before:
![colours-before](https://cloud.githubusercontent.com/assets/29761/2775974/cf7cd020-cacc-11e3-9993-dd0885ce2985.png)

After:
![colours-after](https://cloud.githubusercontent.com/assets/29761/2775975/d3aff3f2-cacc-11e3-9c43-786cfb4db49c.png)