Change top bar colour only in Transparent Header

try it in this way:

.header-scrolled #header_meta {
    background: #080  !important;
}

the header-scrolled class is added at the end of the scrolling process – so this is i think what you want
the transparency of the top menu until scrolling comes to an end.

maybe you have to make some rules for your listpoints in the top bar.

by the way – by using an rgba value you had the choice to make it a bit tranparent with a unique color:

.header-scrolled #header_meta {
    background: rgba(255, 150, 50, 0.5)  !important;
}

you can see it here: http://webers-testseite.de/ikom/neue-seite/

try to explain more precise what you want to achieve.

Btw. it is much easier if we have your testing page.

The changings should only affect the homepage – everything is fine on your other pages with your actual settings ?

the transparency of #header_main_alternate in which the main navigation is placed is in the header container (at the bottom of the header container)
so if this main navigation including container is transparent the background color of header is visible. !

you can try this:

.home #header_main_alternate {
    background: rgba(255, 255, 255, 0.5) ;
    bottom: -50px;
    position: relative;
}

now the main nav sits under the header not over it. But does it realy look good?
look here if this is what you mean: http://webers-testseite.de/ikom/