Change color of menu bar and sub-menu bar

Hello !

I read on the forum the followin does can do this :

/* change menu colour */
#branding #access{
background: #93272E;
}

/* changer sub-menu colour */
#branding ul.menu ul a {
background: #93272E;
}

I put these lines in my CSS…. but it doesn’t work.

How can I make those modifications?

Thanks,

Marc