facebook comments plugin -- how to override the wordpress theme's color

I installed the facebook comments plug-in on a website but the theme's color is overriding the chosen dark background color for the plugin:

The site is: truenode.org.

Scroll down to the bottom to see the plugin. It's all white but it should have a dark border. I've tried adding !important to the plugin's div background color to no avail.

How can I override this?