Submenu: How to change font color or background color

Having some troubles with submenu colors, as you can see at this link:

http://fronteirasbike.com/site/index.php

When you put your mouse over PRODUTOS and over BICICLETAS, you can see that the next ones will be with black background and black fonts... only showing white when putting you mouse over.

What I have to do to change the background color or the font color.

Hi.
You had to change something in .css files because in oryginal template or quickstart everything is ok.