Extra classes for Background Color plugin

I know it is a hacky method, but it does the job for the moment.

By the way, I was looking at the getCssClassName function.
This is a very unreliable method to create classes, as it changes dependending on the amount of instances and position.
I know it is to be sure no style is overridden, but as a front-end developer you are nothing with the 'class' option.