I just commit to GitHub a class based library called JPersona..
You can get the background color and text color of the active persona your Firefox is wearing and to do whatever you want.
This example shows :
0. How to import LightweightThemeManager – the one responsible for handling Personas.
1. How to write class-based library for JetPack
2. How to import this library in your main.js and how to use it.
Go now to github and give me a feedback