Horizontal Login on Menu Bar doesn't line up

Hi. This may be two issues in one, but I'm not sure if there's a simple css solution. I've been trying and am new to all this, but no success. So here's the situation:

I want to make modifications to the horizontal user login. The Horizontal Login Block in the theme's settings is enabled. And I put the User Login field in the Menu Bar Block area. Now the problem is this: the username and password words cannot be seen against the black background, which you can see in the attached photo, userpassblack.png.

Now, I would like to make a modification to the login by changing the "username" "password" words to icons.

If this is not feasible, then I need to be able to make these changes:
* change the color of the words: "username" "password"
* change the background color of the menu bar block
I think these are css changes, but where do I change them?

So, if there's a simple css solution, then how to I make the changes. The attached photo is what I am looking for: newuserpassblack.png Also, I recognize if I want to use icons I would more than likely need to insert them, but where do I place them?

Thanks in advance. BTW, this is a really nice theme, and I've viewed many. I love the many region block areas.