How Do I Make The Sidebar Background Colour Stretch the Full Height of the Page?

Hi,

I am trying to make the colour I have added behind the sidebar stretch the full height of the box it is in - from just below the navbar down to the footer. At the minute it is only stretching as far as the text and then it stops?

Is there some .css I can use to change this?

My site is at 4.biz.