[mcupka]

Hello,

1) To change the background of the main navbar (so instead of the blue you currently have, this will change it black):
.navbar.navbar-inverse.mobile-hidden { background: #000; }

2) Selected page to have a red background:
.navbar-inverse .navbar-nav>li.active>a { background: #FF0000; }

3) Red hover background for dropdown items:
#top-main-menu li li:hover>a, #top-main-menu li li a:hover { background: #FF0000; }

Hope that helps.

EDIT: And to change the current nav hover bg color from blue to whatever:
#top-main-menu>li:hover>a { background: #000; }