XF 1.2 Profile page tabs


I am trying to change the background color on the profile page tabs which are currently active.

.profilePage .tabs.mainTabs li.active a {
background-color: rgba(0, 0, 0, 0);
That is the CSS rule I am trying to change. I am fairly new to Xenforo so I have just been putting my CSS changes in extra.css. I am using Google Chrome and when I make my CSS changes using it, it works fine but as soon as I put the above css in extra.css, it changes nothing.

What am I doing wrong here?