It seems to be a: #imagesList2 class imagesList. Try to give there a border-left property (border-left:1px solid #color;) in your default.css As color use the html color notation.
So, you have 2 possibilities: 1. Easy & dirty: just make a point.bmp (1px x 1px) with wished colour and put it into tamplates/img/ then in default.css give it into #body .container .main #content as a background. background:url('img/point.bmp') repeat-y 750px 0px; The disanvantage: on the pages without right-pictures, the line will be visible, and the text will come over the line. 2. More difficoult, but clean: redesign the template and css. Put the imagesList-div out of #page.