XF 1.4 Login or Signup bar help

How do I change the color of the login bars little line above it, and how do I change the color of its itself.

As you can see if my picture, I want the 'login' red and the bar thingy black so it blends in... How do I change it?

Also, I'd like to know how to change the roundness of the corners of it.

(alternative link http://imgur.com/TgnTnFk )
Is there any css I can put into my extra css for that? i'd like to keep most of my stuff in there incase something ever happens to my site.