Basic code for WPO Primary Menu link and mouseover colours:

/* link colour */
.wpo-nav-menu a {
	color: #333; /* change colour here */
	list-style: none;
	text-decoration: none;
}
/* link hover colour */
.wpo-nav-menu a:hover {
	color: #999; /* change colour here */
	text-decoration: none;
}