Jerrad, the heights of the left and right columns already match the height of the center column. Just add some background color to left and right side and you will gain the same effect.
Add this code to left and right columns(<TD ):
Code:
class"leftcolumn"
class"rightcolumn"
add to skin1.css:
Code:
.leftcolumn{ BACKGROUND-COLOR: #cccccc;}
.rightcolumn{ BACKGROUND-COLOR: #cccccc; }