Add color schemes for OKAY, WARNING and CRITICAL

Hi shutterstock,

I thought it'd be a cool addition to the normal color palettes in order to visualize things like the state of a runnin service.

It is similar to the colors used in minitoring systems like Nagios and Icinga to describe the state of certain monitored elements.

Hope you like it.

Thanks!

![nagios-color-palettes](https://f.cloud.github.com/assets/1198936/46429/350e4998-585d-11e2-919f-6f2bf9dd7c0d.png)