I want to customize them more but i can not find the group identifer or whatever you do it with.

I want it to be able to be customized in CSS. 

But it has to be the username in the database and not just on one page.

You cannot customise the ID (the number), as its an ID. If you are looking to add CSS to a group name, you can actually do that directly within the software. If you go to Members>Groups and edit any group, you will see 'group formatting' where you can choose a color. However if you wish to do more than this, such as wrap it in span tags so you can style that way or even add a CSS class, you can do this by selecting 'Use HTML' at the side of that setting.

@Marc Stridgen Thanks alot this worked.

I did the same thing yesterday but i thought it didn't work. 

I must had done something wrong.

Thanks!