[ThatGreenAlien]

Since usergroup styling is based on the usergroup itself and not the style, you're going to want to use a span class to have a different color for each theme.

Example, in the Edit User page, your prefix and suffix would be...

<span class='member'></span>

and then in the additional.css, throw in...

.member {
color:#fff;
}

and since the additional.css is different for each style, you can change it depending on the colors and so on.