Changing the colors of submenu top border

Hi! Thanks for the theme, its cool

I tried to change submenu’s border-top color, but didnt find where to do that on the theme settings, so i tried to do that with custom css. I inputted following to the custom css field in theme’s settings:

#menu > ul > li > div {
border-top: 2px solid #fff;
}
.custom_menu_4 #menu > ul > li ul > li > a:hover {
background-color: #fff;
}

css does not work even if i put !important