@cseevinck
Can you once try the below CSS code in the Additional CSS box provided via the Customizer Options and check once:-
.tg-primary-menu > div ul li:hover > a {
color: #76c8ae;
}
And for the underline, if you are referring to the same menu, then, can you once try the below CSS code in the Additional CSS box and check once:-
.tg-primary-menu.tg-primary-menu--style-underline > div > ul > li.current_page_item > a::before, .tg-primary-menu.tg-primary-menu--style-underline > div > ul > li.current-menu-item > a::before, .tg-primary-menu.tg-primary-menu--style-left-border > div > ul > li.current_page_item > a::before, .tg-primary-menu.tg-primary-menu--style-left-border > div > ul > li.current-menu-item > a::before, .tg-primary-menu.tg-primary-menu--style-right-border > div > ul > li.current_page_item > a::before, .tg-primary-menu.tg-primary-menu--style-right-border > div > ul > li.current-menu-item > a::before {
background-color: #76c8ae;
}
Thanks.