well guess what...
yeah anyways, logon to your FTP and access this file:
modules/Forums/templates/TEMPLATE_HERE/overall_header.tpl
open it up in a text editor and find the portion where it says
right above it should the the links up top, in html form, easily edited.
to edit the color of that border, find the style.css file (it will be TEMPLATENAME.css) in the same directory as the overall_header.tpl.
find the corresponding border color in that file (i cant really tell what one it would be because i dont know what theme youre using

)