XF 1.3 Group prefix

No, but the red tag, I dont want it to be Sr. but i want it to be marked in the red.
Then you'll need to follow the guide Brogan linked to get the red background for the banner. Enter a custom class name for the banner, then add what you want to the EXTRA.css file.

If you want the username to be in red as well, then you can add your customizations to the "User Name CSS" field.