Lets set a color on panels since a background is already being set

It almost looks like this is the way this mixin was intended to be.  We are setting variables for the panels color in  ```less/variables.less``` however were not using them other than to set the headings color.  Since panels set a background color we should probably set a foreground color.  

This also would fix this issue... http://jsfiddle.net/rwnnwy1b/2/