I don’t really know much about rev slider. From what I can see in that article it looks like what you’re doing with the div should work.
<div style="background-color:{{meta:event_main_color}}" class="primary-background"></div>
What is the class primary-background doing?
Is the div being output properly with the css style?
When you inspect the page is the background color being applied or is it overridden by something else?
