What do you mean it doesn't scale to the bottom? Are you talking about if you included a border on the right that it doesn't go all the way done to the bottom on outer div? I would have the border be created by the content area since it would be the biggest section of your site, or I would hope so.
However, I have to have both blue and green section have 100% thus they both scale down to the bottom of the screen. This means that there might be alot of empty space if the content is not long enough in the green section.
Found a way to solve this problem, but not sure its the optimal way to do so. Here is the code and CSS for it. Basically, I put the background color to the content DIV instead of the leftCol DIV. I also specify a white background color for the rightCol DIV.