[Grace Themes]

Hi Stijn

Go to Appearance -> Editor -> style.css
add below css code at the end of style.css file and change color code as per your need.

.sitenav ul li a:hover, .sitenav ul li.current_page_item a, .sitenav ul li.current-menu-parent a.parent{ background-color:#e15e26;}
h1.entry-title::after { background-color: #e15e26; }

Regards
Grace Themes