Change background color of .MOGRT file?

What seems like such a simple thing is impossible to do as far as I can tell in Premier Pro. Looking at the templates for titles and logo animations, some have a light background, and some have a dark background. I have one that I like on a white background, but would like to make a second version on a black background. I can change everything about the template, except for the background. Why must this be so hard?