theme BLUEMAGIC: how to change border color?

I’ve been customizing the bluemagic theme. I want to change the color of one border (or pair of borders), to a custom color, and I can’t find the setting. It’s the vertical border or line that separates the blog area from the sidebar. It appears on every page, so I assume it must be in style.css, but I can’t find anything that affects that border. You can see the problem HERE. Any suggestions would be greatly appreciated. THANKS.