CSS won't change colour - html

Question

Bought a template, and been working on this for the last couple of days. On my wits end now. I am trying to change the hover over main nav colour and current chosen page colour, to no avail. Please advice?
Code attached.
nav#main-nav {
z-index: 50;
display: block;
}
nav#main-nav ul {
position: relative;
z-index: 49;
margin: 0;
padding: 0;
list-style: none;
}
nav#main-nav ul li {
position: relative;
z-index: 45;
float: left;
margin: 0 0 0 20px;
padding: 0;
}
nav#main-nav > ul > li > a {
display: block;
font-family: Ubuntu;
font-size: 13px;
line-height: 40px;
color: #ffffff;
text-decoration: uppercase;
position: relative;
z-index: 45;
padding: 20px 0;
letter-spacing: 0.1em;
}
nav#main-nav > ul > li:hover {
z-index: 46;
color: #ffffff;
}
nav#main-nav > ul > li.current-menu-item,
nav#main-nav > ul > li.current-menu-ancestor {
color: #ffffff;
text-decoration: underline;
}
nav#main-nav ul li .sub-menu {
position: absolute;
top: 80px;
left: 0px;
width: 200px;
padding: 0;
display: none;
z-index: 47;
}
nav#main-nav ul .sub-menu li {
float: none;
border-top: 1px solid;
margin: 0;
}
nav#main-nav ul .sub-menu li:first-child {
border-top: none;
}
nav#main-nav ul .sub-menu li a {
color: #ffffff;
font-size: 12px;
line-height: 20px;
padding: 10px 20px;
display: block;
}
nav#main-nav ul .sub-menu li:hover {
background-color: #ffffff;
}
nav#main-nav ul .sub-menu li:hover a {
color: #ffffff;
}
nav#main-nav ul .sub-menu li.current-menu-item > a {
color: #ffffff;
text-decoration: underline;
}
nav#main-nav ul li ul li .sub-menu {
border-top: none;
position: absolute;
top: 0px;
left: 201px;
}

Answer 1

You have
nav#main-nav > ul > li:hover {
z-index: 46;
color: #ffffff;
}
The problem is that the anchor has other styles that override the code above. Then, use
nav#main-nav > ul > li:hover { z-index: 46; }
nav#main-nav > ul > li:hover > a {
color: #ffffff;
}