Hi magzaloo,
it’s very simple,
=> Use Below code Menu Fullwidth Background color
#site-navigation {
background-color: #;
}
=> Use Below Code Menu Hover Background-color
.main-navigation li:hover > a {
background-color: #;
}
=> Use Below Code you can change Menu hover Font Color
.main-navigation li:hover > a {
color: #;
}