Do you edit the actual code or does "bg color command" mean a button that you push? Have no idea what Cooler Email is or how it works.
Anyway, you have to use CSS to set background colors to individual items. Since it is a HTML email you are trying to create you'd probably be best off to use the CSS with the style attribute. If you have for instance a DIV (could be anything) that you want to have a red background color...
CODE
<div style="background-color: red; color: white">....</div>