If you look on line 2202 in your css you’ll see the following code that is causing that to happen –
.site-header .genesis-nav-menu .current-menu-item > a,
.site-header .genesis-nav-menu a:hover {
color: #aaa;
}
You can split that code up and add the white font/color to the “current-menu-item” link while leaving the “hover” as gray like this –
.site-header .genesis-nav-menu .current-menu-item > a {
color: #fff;
}
.site-header .genesis-nav-menu a:hover {
color: #aaa;
}