Yes, this can be done via CSS. Here’s some code to illustrate how this can be done:
#masthead {
background-color: red;
}
.menu-toggle,
.main-navigation,
.main-small-navigation .menu {
background-color: transparent;
}
.menu-toggle,
.main-small-navigation a,
.main-small-navigation a:visited {
color: green;
}
.main-navigation ul a,
.main-navigation ul a:hover {
color: yellow;
}
This is pretty ugly though :) It’s just for demonstration, though. You can change the colors to ones that you feel are appropriate. If you have colors in mind just lets us know and we will integrate them for you.