You can add it in around line 1927 inside here –
.genesis-nav-menu.responsive-menu li.current-menu-item > a,
.genesis-nav-menu.responsive-menu .sub-menu li.current-menu-item > a:hover,
.genesis-nav-menu.responsive-menu li a,
.genesis-nav-menu.responsive-menu li a:hover {
background: none;
border: none;
display: block;
padding: 10px 0;
text-transform: none;
}
You may have to add !important if the color doesn’t show up since this is overriding it –
.front-page .genesis-nav-menu > .menu-item > a {
color: #FFF;
}