I will teach you how to fish that way you can catch stuff you need lol... :)   Tools are wonderful when dealing with css. 

So in Firefox (ie's version sucks) bring up the forum page or any page you want to check out. Then in FF open up the drop down box (the one with options and help listed in side it) and then open up the webdeveloper drop box and click inspector.  

This will allow you to move a box all around the page and you can lock on the item you want by clicking on the item, unlock by clicking the little arrow thing. 

This will tell you the css that controls the visuals on the page and better yet, that particular item.  And then go into ow_themes and open your css file and find that value.  If it is not there then look in the origin theme because that is the default.  

Hope that helps.. :) 

Also this needs to be moved to the customize code section of the forum by a team member please ;)

no no the css is in your theme folder,  use notepad, or programmers notepad (never ever use word processing software to open coding files - it leave hidden code inside) 

so use one of those to open your css file in your theme, i think its called base.css and edit the code in there.  

when your done, then refresh your cache in order to update the static files.