Why are you doing it in forum home?, you simply need to go to the Usergroup manager>Administrators>Edit and in the portion where it says Username HTML Markup enter this in the first box
HTML Code:
<span style="font-weight: bold;color:blue" title="Forum Admin">
and put this in the second box
Now admins will be seen in blue everywhere and when you mouse over their name they will show the title "Forum Admin"